An old meme used to make fun of kids.
Only dumb kids would take this sentence seriously, after all.
Gotta say though, I miss the times when "redpill" actually meant something. It was fun in 2015 or what year was it.
Most pictures with this tag have been "retroactively" tagged years after being uploaded.
It could be considered tag vandalism since it's a stale joke that didn't even exist at the time those pictures were made, but to be honest I (one of the admins) find it entertaining for the reasons stated above, so here we are.