This isn’t hypocritical at all.
As a straight man, I’m not attracted to dudes, so in ‘normal’ relationships, the man is always the worst part of it.
Shotas, however, are cute and not gross, disgusting adult men with body hair and lumpy bodies.
So Onee x shota is good cause there’s a hot girl and a cute boy.
Ojii x loli is bad cause it’s a gross dude and a... like, a little girl. I can’t lewd that.