Most consumer windows PC owners pirate apps. Anecdotal evidence, of course, but for every one who's keen on paying for software there's 10 who will call a "techie" friend up and ask where they can get a free version.
That isn't even an anecdote, so I would probably classify it as a "baseless assertion" rather than "anecdotal evidence."
If you have no real evidence for this assertion, then why do you even try to make the argument in the first place? Couldn't you just use that same logic for Mac users?