I completely disagree and think it's very well defined. For instance in r/nyc I was downvoted for leaving a comment saying how I wouldn't vote for a candidate voting against John Crowley in Queens because part of her campaign is the abolishment of ICE. This to me is idiotic politics (I get that the intention is to move the Overton window to the left) and I was downvoted to oblivion on reddit. Stuff like this is idea suppression.

At the risk of saying 'both sides are bad' I would point out that this behavior is not limited to American conservatives. Politics in the US is extremely tribal.

It’s definitely not limited to one side but I think America’s general historical right lean means that calling something “left-wing” has carried more of a stigma and is thus more common. Even a fair number of people who like liberal/socialist get uneasy about being called lefties since that brings in a lot of Cold War baggage.