The real problem here is what person A is actually thinking, and the invisibility of that process to themselves.

In brief, Tu quoque.

As an A, I'll tell you what my deluded perceptions are of my internal dialogue. If I say "you're wrong, because blah blah", that's because I am presuming you can handle the truth, otherwise I wouldn't bother offering my comment, as indicated by the original poster.

person A : meh, person B can't handle the truth, I'll just shut up and say nothing.

That's what you do when you think the person can't handle the truth - you shrug and move on.

I think I've identified two Person A values relevant to this discussion:
Expressing honest disagreement is a sign of respect.
Crafting that disagreement to manage feelings is a sign of disrespect.

Two different species - those who manipulate things, and those who manipulate people. They don't get along too well. There's probably a third that does both, but I don't think they're large in number.