DOTA games have really terrible communities in general, though LoL is relatively nicer in comparison (but only because HoN/DotA guys tend to be real asshats, lol). The thing about Dota 2 is that people have been playing Dota for the better part of a decade, so from a player perspective there are just some basic concepts that you assume people will know, and it's very frustrating when they don't. It doesn't help that there's such a steep learning curve for a new player, since basic competency requires you to know all of the 100+ heroes and all of the items, not to mention the actual strategy. People are just a lot harsher in these games since it only takes one player to completely ruin a game, which can be an hour-long time investment.
Buuuuuuuut, to answer your question, LoL is designed to be an easier game to get into for sure. There are a lot of aspects streamlined, the map is simpler, there are no denies, and deaths are not punished as heavily. That's not to say that I think the game is a dumbed-down version of DOTA (though diehard DOTA/HoN fans would certainly argue that); it's a very different game though in the same small sub-genre. As I said before, if you actually liked Rise of the Immortals (yuck), you will LOVE either Dota 2 or LoL.
