For punishments to be just, they must be merited, consistently enforced, predictable, and proportionate.
Perhaps showing support, even accidentally, for reactionary views might merit punishment. However, this punishment is likely not consistently enforced, and the rule is not stated anywhere on the website.
Most importantly, any kind of ban for a single upbear from a user with no prior pattern of behaviour is entirely disproportionate to the wrongdoing. It blows my mind that anyone could consider it an appropriate response.