I don't know how long this will be, probably short. But truth be told I came to a realization today.
A huge competition between LoL and Dota2 paints both fandoms as whiney biggots. "Noob" this or "Scrub" that, "LoL sux" or "Dota's 4 casuals"
..It's just Youtube.
In game, on Reddit, literally everywhere else where both games can be mentioned, everyone's open minded and happy laughing and playing. There are always a few ragers but you get that in all games. On reddit I can get upvoted on /r/leagueoflegends for saying what I like about Dota and would enjoy seeing in LoL and vice versa. There's some amazing artwork crossovers drawn of the two games.
Where was the last place you actually saw a flame war over the two? I'm willing to bet 90% it was in Youtube comments.
So yes, who has the worst community? LoL or Dota? It's nether, it's Youtube.