1) "Support the troops" - This is typically used when someone opposes a military deployment (a war). When someone opposes a war, that person should say that no, they don't support the troops. Because the troops are doing something they oppose. They mostly, and more properly oppose the political and policy decisions that resulted in someone demanding the troops do something they felt was inappropriate, destructive, or generally foolish and not helpful to American interests and security. But basically we should not say blandly "I support the troops". Because that implies we support the mission they are deployed for.
2) "I regret offending people" style non-apology apologies. If what you said or did was what you wanted to say or do, you don't actually regret that someone was pissed off by it. What you regret if it offended people and that reaction upset you was that you said or did something stupid (and were caught doing so). In most cases, this is not actually a regret people are experiencing that others were offended. They just want people to shut up about it and move on. I appreciate that these public displays of passive aggression in response to accumulated grievances are sometimes amusing and even warranted as a way of getting back at such complaints, but if you didn't want to apologize, it may be better to just not acknowledge it at all than to make an insincere attempt to mollify some people. If you really do want to apologize, then find a way to say it that acknowledges you may have actually been striving to learn and understand the complaints of others rather than stating the mere existence that there are complaints and grievances against some statement or action. Which you apparently either don't care about or understand.
3) "If you don't have something nice to say don't say anything at all" - Almost nobody actually follows this. Our primary form of moral reinforcement as a species is dishing dirt on other people or complaining about other people. This is far, far more common than hearing about something awesome someone else did as an exemplar. We should admit this hypocrisy and instead of telling people what not to do in as far as not saying bad things, we should strive to pay more compliments to balance out our tendency to try to do violence to other people's reputations in the trading of gossip and information on the flaws and peccadilloes of others. (Our own flaws are a different variety of currency).
Addendum point to 3: This also infects superhero movies. Where it is far more common for such movies to tell us "this person is a hero" than to actually attempt to demonstrate it as an example to hold up toward. Batman in some respects may be the exception and GotG also had elements of this. Superman movies have not (at least not for a while). The most "heroic" character was typically Jor-El, and not Superman. One reason for this is that movies that involve self-sacrifice, or acts of devotion to and protection of others, probably won't involve as many explosions. Science fiction movies have struggled with this also since probably Empire Strikes Back and some of the earlier Star Trek films (since the Borg, it's been lackluster there too). What's typically portrayed instead of acts of heroism is acts of recklessness that because of the deus ex machina and plot armor effects, are pulled off. Showing exemplars in media is apparently very hard to do, and I would bet this is because we don't spend very much of our time and energy talking about and holding up exemplary behavior in others.
4) "Some of my best friends are.." First. They're not some of your best friends. Everyone knows that in most cases except the person saying it who is holding them up as a token talisman that somehow excuses something else (using another person to protect yourself is not typically viewed an act of friendship). Second, it's irrelevant as the topic is typically either some nonsensical statement Person A has made that doesn't involve or impact their "good friend" Person B or the topic is some variety of public policy position which is informed not by a random sampling of people potentially impacted by the policy but by Person B style friends who have become so by not saying anything inoffensive to which you would disagree (in your presence). Most of us do not select diverse grouping of friends so that we can say "some of my best friends are". We select actually fairly homogeneous groups of friends who affirm our pre-existing beliefs rather than challenge them. What happens when we befriend people who are often of different and distinct beliefs and views is we may adopt portions of their views or moderate some of our own more extreme views (this is typical of people who suddenly realize they have an atheist or gay friend). Most people do not however set out to meet people for the purpose of having a set of friends that includes "person from stereotypical group B", and "person from stereotypical group X, which is very different from our group C", this is an accident of our lives and is not a defence of having said anything about any other group of people.
5) "Police have a difficult job, etc". This might be partially true in the same way the "support the troops" mantra has a grain of truth to it, but there are several problems with it. First it obscures that one of the reasons police have a "difficult job" is that current laws are often expansive, covering a great deal of human activity, and as such allow a great deal of leeway for police to detain and arrest people, where if laws were not as expansive police would have less latitude in who they arrest and detain. But police also have a great deal of discretion not to arrest and detain people by that same token and are therefore choosing to arrest and detain people, or choosing which people they wish to arrest and detain and which they will ignore. Some of that exercise in prejudice will be fueled by actual biases and animus toward others. Second some of the same laws should protect police already if they do things which are appropriate in the context of their duties. Self-defence law for instance should allow for an officer to have killed someone in certain contexts, which are mostly the same contexts that would permit any ordinary citizen to do so. Police are also often further insulated by law and by contracts and training in the language of the law from penalties for making inappropriate arrests or a variety of citizen complaints about their work on top of the disturbing lack of penalties for acts of violence and brutality. Third police themselves have made their jobs much harder by accommodating some of the poor incentives to enforce some laws (vice crimes and a variety of discretionary crimes that typically issue fines) by tending to come off as an occupying force in many neighbourhoods and towns across the country in the methods and tactics they use to enforce the law. "Good officers" deserve little public sympathy if they typically try to not only protect these other officers for indecent behaviors but reward it.