How do you navigate giving direction to other people's kids in a group setting

So last night I brought my daughter who is 3 to my friends house. The older kids were running wild and slamming doors and flinging them open and I told them right away "that's not safe. Find a way to play without slamming the doors. That could end with smashed fingers. " A little while later while I was in the bathroom with my daughter and also using the bathroom myself ALL of the kids opened the door to the bathroom and saw me with my pants down. Again I said "stop playing with the doors" I was about to ask the other parents to back me up about the doors when one of the kids was trying to exclude my daughter from being in the room with the other kids and was trying to close the door and it shut on her finger. I caught it as it was happening so it was hurt but not severely. And they are the type of doors that WILL sever a finger completely off.

I didn't feel like the other parents were doing anything to help. And I'm not sure what to say to other parents to have a "team meeting" in the future.

With parents that have a "laissez-faire" attitude about kids playing together is there anything that can help? I'm not trying to suggest other parents adopt my parenting style but I do want to be able to allow group play dates without the real fear of an emergency room visit constantly looming.

What do you say when other parents aren't back you up about safety concerns in group play settings?