"I am not a vegetarian because I love meat."
Translation:Jeg er ikke en vegetar fordi jeg elsker kød.
I used to think the same. Then I became a vegan and found out I can do very well without it. It kinda scares me when people say that; I hate to think what would happen if they ever ate human meat.
Hvorfor kan jeg ikke bruge "ingen" her? Fx. "Jeg er ingen vegetar fordi jeg elsker kød"
You should be able to use "ingen". Few people do in a sentence like this, but it is fully valid to do so.
"fordi jeg har gerne kød" doesn't make any sense. "fordi jeg gerne vil have kød" is probably what you're trying to say, which is fine (but it's not a correct translation of this sentence).