(Long text warning)
I know why: Because of the simple differences of MSMG and AUB/fun. AUB and fun rather see meme creation and being on the hot page as a competition, and they hate it when a low effort meme such as upvote begging gets to the hot page. MSMG however doesn't care about huge effort, and they just chill with each other, which is why upvote begging is accepted.
But now to the actual reasons of the conflict:
1. MSMG sees the hate on upvote begging of fun and AUB as their weakness. This is why they post upvote begging in fun, resulting in fun and AUB users getting mad, resulting in MSMG users making fun of these users and laughing their asses off. (This is also known as ragebait)
2. Like I already said, MSMG is completely ok with upvote begging, but they don't like it when AUB users cross up and think they can make the rules.
3. A lot of AUB users sometimes act cringe and immature when they see upvote begging, like DavidStevens below this image (it was posted in MSMG):
imgflip.com/gif/92qb1b
But one thing I agree in with you: The upvote begging in the fun stream has gone a bit too far. I used to be pretty active in trolling the fun streamers, but now I start having respect and understand totally if fun streamers want to see more memes that make them laugh.
So tl;dr: MSMG users dislike you because of different opinions about upvote begging and you making yourself an easy target for trolling. So the best way to deal with upvote beggars is ignoring them.