He's just jealous that nobody takes his finger painting skills seriously. That or he's just angry that you turned him down to be his girlfriend. Pay him no mind and eventually he'll get the hint that he should walk away.
His art really isn't that bad (though there are a lot of far less douchelike folks here that blow him out of the water), and his 'rules' aren't really super off base. It's just the hyper-narcissistic presentation that makes it rageworthy. 10/10 would frown deeply again
Her post wasn't written in a helpful and constructive light, but to boast her 'talents' and lift her so-called ego, so I have to agree with you here. I hate proud artists who are so full of themselves. Nobody has the right to tell you that you are not an artist, only you, yourself can make that call.
She does have some talent, but man oh man she has a long way to go, her fundamentals are very lacking. If one builds a house on sand, it will collapse, same applies with art. Don't take what she said to heart, because as we know, empty vessels make the most sound