[jholman]

> When someone is called crazy, they're making a parallel to a crazy person on a train screaming about how they didn't take their meds.

I do not agree that this is what is intended, or heard, by the overwhelming majority of speakers of English, when that word is used. It seems to me, with a great deal of (fallible) confidence, that people usually mean something much less extreme.

> When someone who has legitimate mental health issues is called crazy, it makes light of a very serious issue

I do not agree that it makes light of the issue. I don't understand what is light-making about it. I do think that it puts the problem in a tidy pigeonhole, which the actual problem probably doesn't fit into. But people do not have infinite cognitive resources, and so they oversimplify things when they think they can get away with it, and as far as I can tell, this is one of those cases. That's not "making light", it's just "not paying a ton of attention".

Perhaps I'm wrong about either of both of those things. That would be a powerful and relevant-to-my-interests case for you to make, and were to you be successful at updating my belief, I would be grateful.