So long as you are clear and respectful, they can't say anything against you(If they respond rudely then report them. If they aren't being rude then there shouldn't be an issue). You have every right not to like Charizard, you however can't insult it or cause a situation which would likely turn into something bad. You could have said something more along the lines of "I'm not interested in Charizard, I'll be glad when it's gone", while it may still receive negative responses, it's less likely to cause a problem and they can be punished if they are being rude anyways. Just make sure your posts are respectful and everything should be fine.