Guess what, your teacher is human. Humans make errors in judgement. Supposing that he's basing statements from experience, did it ever occur to him, or you that those "junk" MK4s were poorly maintained, female owned (not sexist, but MOST females know nothing about car maintenance), or beaten to death?
Another thing to add: Your mechanic has been wrenching for 50 years? That makes him 70+?
MOST (not all) older folks have brand loyalty and prefer American cars over foreign. You wanna bash a brand or product? That's fine, but at least know WTF you're talking about.
Your mechanic is entitled to his opinions, I have a right to tell him how stupid his opinions are.