well we don't really have much of a relationship...but it wasn't just bad language. he was talking to some guy adn they were saying things that are....just...bad...
I'm not sure what kind of things that are just bad you are speaking of, but I get the feeling from your post that you think your little brother might be getting himself into a bad or even dangerous situation. If you at all suspect that he is endangering himself in any way, such as giving private information to an older person over the internet or talking about hurting himself or someone else, etc., you NEED to tell your mother. Now.

It is much better to have your brother angry with you for a little while than to have him missing, kidnapped, in trouble with the law ... or worse.

I'm just guessing here, and I may be wrong, but it sounds to me like you are very concerned about this conversation, but don't want to post what it was about specifically in public. That's fine. But if you are that concerned, please tell your mom and let her handle it.