For me the age gap between Mark and Nikki makes him seem creepier.. Of course he could try to pull the same crap with a woman his age but IDK, something about a man doing it to a woman 40 years his junior just looks terrible. Plus, remember he said he didn't want a woman over 35? And his reasons why? Ugh.
I know a few couples with an age gap, and they seem to have healthy, equal relationships. Mark just seems to use his age to treat her like a child, as evidenced by his comments.