It's not about whether there is any astroturfing going on, it's preemptively calling it out, implying that everyone who disagrees is astroturfing.

It's similar to people who say things like "I know I'm going to get downvoted, but". Instead of making assumptions about the nature of a discussion in a comment people should wait for the discussion to develop before judging.

If you know someone is astroturfing call it out. If a post isn't appropriate or isn't contributing to the discussion call that out. Just don't assume that people are participating in bad faith, especially before that participation has even occurred.