I’m not so sure. The study discusses specifically people who engage in partisan subreddits, which is not the same as being politically engaged. It also uses an AI to grade toxicity, which surely mischaracterizes many interactions.
For example, I have been in communities of a non-political nature, where political discussions occur. These are often about real issues that affect real people in the community, and yet there are people complaining about political content.
To complain about political content is, at best, a very privileged take, demonstrating that you are in a position where politics do not affect you much. At worst, it is actively hostile behavior with the goal of continuing the status quo and shutting down discourse. I would call most of these kinds of comments “toxic”, and yet the rhetoric is usually fine, so I doubt an AI would agree.