It feels like the only reason to label one side of the political spectrum "reactionary" in this way is to poison the well for anyone responding to you.

Where as, pre-labeling things as being politically one-sided is very reactionary, and seems to be what you're doing here. It's also not limited to just one side of the political spectrum. I would argue that Conservatives tend to be even more reactionary than liberals. See: All the legislation to prevent children from eating from dog/cat bowls in schools when there's no evidence of this occurring.