When starting off writing poems, should you avoid dark/deep material?

I've always wanted to start writing poems but I was put off by a guy at a poetry session in school. He said that when he was a teenager, when teenagers writes deep and dark material it tends to be crap, hence why you should start with light hearted and crude poems. He read us his poems, they included material such as: cheetos colored skin, "do pigs like s@&€? Does pinnochio have a wooden d¥%#?" And he kept talking about poop and urinals. It put me off that he said that young and inexperienced people can't write deep and dark poetry. I've tried writing several times, but it sounds so pretentious with each poem I write, maybe he was right.