Most complaints about other members come from people worried about their status.
Let’s imagine someone you know and trust complains about a post by a newcomer. The complaint here is probably less about the post and more about a threat to status.
Your friend is worried their status is under threat. Either the newcomer challenged something they said or is rising in popularity and might overtake their own status.
Whether you remove the post or not, the same thing is going to happen. Soon either more people will complain about the newcomer (friends of your friend) or the person who made the complaint will make more complaints to protect their status.
King Of Kong
This evening watch King of Kong.
Look at the social dynamics taking place here. One man is trying to take the Pac Man world record. The existing champion uses his relationships and reputation to stop him.
Everyone acts how they naturally should. They treat the strange newcomer as a threat and close ranks to protect their current champion.
This is the problem you’re going to face a lot.
Existing members will take actions they feel are fair to attack threats to their status. People who like that member will agree with them. This creates the appearance of consensus and creates pressure for you to act against the newcomer.
And this is exactly what you shouldn’t do.
The better option is to tackle the status problem at its root core. Flatter the current member to reaffirm their status and highlight positive values (you’ve always been great at helping newcomers get involved in the group) which they can then internalise.
You will probably find you can act accordingly.
Just don’t become the sword that smites down every threat to the status of your best friends in the group.