How Can I Get My Parents To Accept A Wide Age Gap In Dating?

I introduced my gf to my parents, who met my gf by accident because of a situation where I had to meet them to drop something off while I was with her, and they met her and because of the age difference, they had to give a very shall we say... 'Guess Who's Coming To Dinner' parent reaction to it.

What's the best way to get your parents to accept the age gap though? I mean should I tell them that not everything about an SO is going to be perfect and a gf is always going to have some flaw, just like how my parents wouldn't see each other as absolutely perfect in every way? Or is that not the best approach?