[koube]

Taking a position has a high social cost. Try defending any candidate and you'll get a 10 comment chain where you have to defend your position against multiple internet commenters who are arguing mutually exclusive positions against you but not against each other. These kind of comment chains generally devolve into the every issue and often touches on the history of mankind and the nature of government.

Both sides-ism has a low social cost. Everyone is bad to some extent, this can always be true in a vacuous sense, nobody is offended. You are not partisan nor biased if everyone is bad. If someone questions you you can infinitely motte-bailey backwards into an agreeable position, just by saying you are actually taking no position.