OP, unfortunately there are people with very poor social and communication skills who end up in positions of authority, and some of them abuse that authority. The more mature approach would have been to speak to you about the issue instead of simply kicking you. But for people like that, ignoring difficult conversations is the easier option.
I've been in a very similar situation myself. As others have already said, the best thing you can do is forget about it and move on. If that's the kind of "mature" leadership running the guild, you're probably better off without them.
One other thing: don't expect your guild "friends" to stand up for you. When something similar happened to me, I received plenty of private messages saying people agreed with me, but nobody was willing to speak up publicly. Most people don't want to risk getting kicked themselves.
Move on, find a better guild, and don't give it any more of your time.
Whilst I do think that there is a maturity problem within guilds (though I understand this is also a video game), we also don’t know the full story here. Maybe it was a final straw situation or maybe it was an emotional reaction because of intense circumstances. If it was final straw, it should’ve been communicated clearly and if it was the latter, then that’s not an excuse. But I bring this up on the matter of we can’t properly judge without full context. Maybe this person is mature 99% of the time and this time just snapped, we don’t know.