He did not attack specific people or clearly identifiable subgroups or minorities. He attacked a broad category of people for holding certain views. I think that is well within what is acceptable in online debate.

If you are going to attack this argument, then you might as well say it is unacceptable to call people who favor cutting off hands of thieves for barbaric. Sure you characterize people with a mean word "barbaric", but it you are not singling out particular people only those holding such views.