I think the average age of Reddit is 16. High school students have infiltrated it ages ago. This is why I don't take anything I read in the comment section too seriously.
As you can see, Reddit is overwhelmingly 25-44. The most represented group is actually 35-44. The high school demographic is negligible, and equal to the 65+ demographic.
Also, if you were to be completely honest with yourself, I bet you would not have made the comment you've made if the jokes and the upvotes were about race and lynchings instead of underage girls and rape.