Godamn kids and there rap.
Anybody can do it
ring a ding ding dong,
im playin ping pong,
I blast a gat,
rat a tat tat,
check out my stupid oversized hat
Yea that's some shitty rap. I'll give you this, today's rap is very similar to that...but if you truly believe that all rap is that easy, you come off pretty ignorant. You obviously have never listened to the lyrics of Nas, Wu-Tang Clan, Big L, Immortal Technique, and lots of other (most are from the 90s). Not all rap songs are as simple-minded as the "roses are red violets are blue" type songs, if you read the lyrics from songs from the afformentioned hip hop artists, you would realize that it is purely just very well written poetry (it also helps you are familiar with the slang they are using...even Shakespeare used slang). Good rappers don't use simple rhyming schemes like you suggested. Top it off with the ability to flow and freestyle rather than just reading it straight off the paper, and you got some extremely talented people out there.
The arguement you're trying to use is so cliche and played out and makes you sound like a stereotypical ignorant hillbilly, because you can easily be disproven by a song such as this one:
Prove to me you can write a song/poem even half as good as this one, and I'll agree that "anyone can rap".