It’s not a perfect rule by any means but I tend to believe the friendliness of a community (at least outside of specific circles/guilds/cliques) is inversely proportional to its sweatiness/tryhardness.
This is not to be confused with the community’s competitiveness — they can be competitive yet welcoming and grounded. The problem stems from players who want to be seen as competitive but don’t have the chops to just do it and instead have to resort to punching down at noobs and players who don’t particularly care to shoot for being top dog to feel better about themselves.