Always attack the analogy, never the argument.

I see you've played "internet" before...

He did attack the argument - he argued reductio ad absurdum that classifying "democratic" as "open to everyone" wouldn't be a sensible definition, because the argument would set such a high bar for democracy that no state is democratic.

The irony of this comment is that leaning back and snarkily accusing someone of "playing internet" is precisely the kind of disengagement you're complaining about.