Seriously, I cant seem to figure out why people think that posting "DONT POST HERE UNLESS YOUR IN THIS CLAN" or "DONT FLAME ME!" will stop others from posting. Its not like you have any power over who posts on your topic.
By making a topic, anyone is entitled to post anything they want on that topic unless it violates the forum rules. In fact, posting something like that often makes people do the opposite of what you say just to piss you off.
So honestly, there is no point in saying it. Because if you do, people either are not going to listen, or flame you more.