Not really a friend, more so a fan of his old work that stayed behind because I think he's legit chill.
Tell him to go fuck off. If he persists, he's obviously fucking stupid. Mark is at that point where he's desensitized by all these SMBZ fanboys, so it's best to just ignore them. Hell, the last time he commented on the series was when someone tried to "make a sequel" and it was shit. Most of the people still desperately pining for SMBZ at this point are obviously too far deep in the rabbit hole to discuss with, so you'd just be wasting your time.