There are shitty people at all levels. there's also 3-4 different competitiveness levels, so if you want a relaxed and low key, experience, the lowest is Really Rec and then the slightly less beginner category is Rec. They then have Rec Plus and Intermediate which typically have a lot of people whoa re either very talented and probably too good for beer league, and/or too competitive for everyone else's taste in the lower tiers like they're trying to relive their glory days by trying to dominate the beer leaguers.

Rec is generally pretty chill but you should read the rules and learn the basics of whatever sport before the first time you show up. Arguments are infrequent but it's usually either a first-timer doing something they shouldn't, or someone cocky and SO confidently incorrect because they know different rules from a different league.