While your intentions may be to warn others, the Forums may not be used to to make accusations about other players or clans by name.
As there is no way on the forums to present the necessary evidence from Jagex's systems to support any accusations, here is just comes down to one player's word against another.
Hopefully you used the in-game Report Feature to report what was said in the clan chat, as that will have provided Jagex with the evidence they need from their own systems to be able to take action.
You might also want to look into adding the Authenticator to your account and making sure that you have 2-factor authentication enabled on your registered email account.