The most rude group of teens I ever encountered at either park was at the "Night of Joy" at Magic Kingdom. We didn't know that was going on that night and had been at the park all day when that crowd descended.
You encountered this group at MK, didn't know about Night of Joy but the crowd descended???

Night of Joy is a hard-ticketed event. The park closes at 6pm to the public

and reopens for paid ticket holders at 7:30pm.

(need a stampede smilie here)
We have 3 (older) teens and absolutely love, love, LOVE this age. However, we like them in smaller doses, like fewer than 20 at a time. Huge crowds of largely unchaperoned teenagers are, plain and simple, a hassle for everyone else to deal with. When the numbers are enormous, the minority of obnoxious teens amount to a big number and even irritate many of the fun teens. Sometimes, we barely tolerate events like Night of Joy, Grad Night, concert nights at other amusement parks.
While I think local teens and young adults gravitate more toward USO than WDW, the bulk of visitors to both theme park destinations seems to be vacationers, IMO. So, unlike more seasonal amusement parks (Six Flags, Cedar Point, etc.), neither USO nor WDW attracts the kinds of roving teen gangs that can be a problem at some other places. Just adding my 2¢.