I am happy to have a productive discussion with anyone who is willing to engage in one. If you are not, that is your decision.
If accusers reliably made this distinction, it would probably help. @TroutMan didn’t. But still, if you accused someone of being an idiot, or even just of saying really dumb things, wouldn’t you expect them to be offended? Maybe if you did the latter nicely, to a friend, it would go okay, but to someone you are arguing with, accompanied by personal insults? It’s not going to lead to anything constructive.
I think there is a bit of equivocation going on here. The claim is that calling someone a racist could start a productive discussion, and no one should be offended by it. Yet in practice, in the Pit we almost always see such accusations accompanied by personal insults, and it is certainly not made clear that the first meaning is the one intended.
Productive discussions, if they are going to happen, almost always happen in the original thread. An accusation of being deliberately racist is not intended to spark such, it is merely intended as an insult. It is ridiculous to pretend there is some higher purpose.
Not in my experience. This goes back to some people on the left using such accusations as a political tool. Instead of trying to persuade others that their opinion is the correct one, certain people simply claim that alternative views are racist/sexist/whatever and therefore it is unacceptable to argue for them. The point of the accusation is to end debate, not spark it.
In the case of using a particular word or phrase, it’s a bit different, because sometimes there is a good reason to stop using it. But a. the changes demanded are often petty and not-universally-agreed-on by the group in question, b. they make life harder for those outside a particular well-educated left-wing subculture, c. they are sometimes used to push a particular ideological position, d. as @Sam_Stone said, the outrage is often selective and hypocritical (though I believe you are one of the few posters who actually does try to avoid hypocrisy on this issue). That could to lead to a reasonable discussion, but in general the people who bring it up are not prepared to engage in one. Their expectation is immediate acquiescence and possibly an apology, and any other response is considered more evidence of 'ism’s.