Yesterday I walk in the front door of an obvious trick pad.  One I’ve been too several times and is NICE. I’m introducing myself and suddenly, from a room being used, we hear the girl being pounded.  You could hear each thrust, the slapping of flesh.  She was crying out, “please not so hard, be easy.”  But it continued.  My provider and I looked at one another and I asked, “is she ok?”  She shrugged her shoulders and we went into our room.  Either the girl was putting on quite a show, or, she was getting the life f....out of her.  When would you consider intervening ?

WTF is a "trick pad"? Are you talking about a motel?

Unless there were screams of terror, including words to the effect of "somebody help me" or "get off me and get out of here" I would have done as you did and minded my own business. Can you even imagine the embarrassment you would feel if you kicked the door down like Superman, ready to save the damsel in distress, only to find yourself breaking up two consenting adults involved in role play, or simply engaging in consensual rough sex.

... Mickey Roarke heard this couple argueing behind closed doors in a fleabag SRO. He burst in with intention of protecting the woman only to have her tell him to go fuck himself. So yeah, unless there are screams for help you never know.

Here's how being a hero worked out for Sir Launcelot: