I think they are saying that without the core Lemmy team, there wouldn't be a platform for Sync to build off of (or Kbin, but same thing applies). There's obvious truth in that statement, but I don't think it's a reason to belittle people for being willing to pay for an app. However in OP's case here, (at least without the edit) it does kind of come across as a "fuck you" to the actual platform that Sync is using. Probably not his intention, but perception is reality.

If anything though, we should be reminding people of this and asking them to consider also donating to the continued development of Lemmy or to the running of the instance they use. Not sure why there's this huge circlejerk about people paying for Sync. Let people do what they want...