Simply mentioning a group doesn’t automatically mean discrimination against that group.
What discrimination has been committed against 18-24 year olds because of this post? Was anyone fired? Injured? Killed? Kicked out of their housing? What’s the actual harm you’re upset about here?
Except OP didn’t say they DON’T vote. They said they were LEAST LIKELY to, which you just confirmed with data.
So either you and OP are both ageist for pointing that out or neither of you are.