hmmmm to me, looking wasn't the wisest thing to do in the first place. But I am of the opinion that yeah, maybe it was the right thing to do to tell your friend. You didnt interfere directly with him or the girlfriend, you voiced your concern to a mutual third party to do with what she thought appropriate. Unless he is seeking treatment for his abusive behaviour then he wont suddenly stop and to me it is akin to knowing that someone is abusing a child and doing nothing about it.

So to me, no you shouldnt have looked for your own personal well being, but you acted appropriately according to the information you have. That is JMHO. Now stop looking