If a dude is pursuing a much younger/older dude he really owes no explanation for this. It is his life, and he is free to invest his energy, time and money as he sees fit.
I have been friends with a few guys in my college days who were dating much older guys. Sure, money, travel, clothes, financial benefits played a role, too.
Couple of them, I am still in touch with are now pursuing much younger dudes. In a manner of speaking, they are enjoying the reverse roles. No harm done.
You come across younger guys who are attractive, and have had no problems with hooking up with the guys in their peer group. You hook up, have sex. Move on, hook up, have sex... At the end of the day, a few of those dudes simply feel unappreciated, and start craving for a guy who'll spend some time with them, show them that he cares, etc. True or not, they go with the older guys for the whole range of benefits. It ain't that different in the straight world either.
I see little virtue in policing the sexuality of people I know. They do things for a reason. It is their life, and they are calling the shots.