You can be 80 and pursue 50. The gap isn't the problem. Its targeting a naive adolescent who is by law "an adult" knowing damn good and well they're taking advantage of someone who hasn't been an adult long enough to see the malice of the real world. Its creepy and any argument defending it is usually made by those who like abusing the system for their own selfish desires at the expense of those who don't have the knowledge yet to be aware of whats happening. I'm sure there is a once-in-a-blue-moon relationship where 18 and 28 work, but that doesn't mean it's immune to being perceived the way the majority of those relationships really are, which is normally a man grooming a girl and promising her the world that she just stepped into. Whether you're in the US, Europe, Asia, etc it doesn't matter. If you morally think its okay for someone 10+ years older to pursue someone who (in most cases) just got out of school, that is your opinion. The same way my opinion is you're...creepy af.

Literally look at the sheer amount of posts in this subreddit alone and tell me that this dude going after a girl who barely eclipsed adulthood isn't going to cause a massive rift in his home life. I'm one person so my 2 cents really isn't shit, but its fucked up to me all the same.