Would I give up entirely because of one person? Not at all. However, I would make a mental note (and actually have done so several times) not to help that person ever again. There are plenty of other people here who deserve my time. :)

Perhaps it was a misunderstanding, because the learner may not use the correct words, so this can sound rude to a native?

Just to add, it is not always the learner who gives thumbs downs to corrections. 

I wouldn't stop correcting entries, I would stop correcting HIS ones

No, to be honest I don't do it to help others, I actually do it because I like it. It's a stupid hobby, I know :S

It's not about thumbs down. It's about swear words. Specially when that person claims to be majoring in Spanish, but his Spanish is really poor.