Are Vanitygen less safe than random Adresses since they were bruteforced?
No.
if Vanitygen would always start a bruteforce from 0000000
It doesn't.
Think of it this way: instead of generating 1 random private key, you generate a billion random private keys. Then, you choose the one address you like, and use the private key that belongs to it. In the end, you still end up with a random private key.