There's no rule which governs what type of force police can use. Also, the rules state:
They don't have to ask why people are wanted.
That's to avoid people getting tazed, shouting 'unwant me, self defense!' and then not knowing what to do. They could be lying, and even if it was self defense, the crime of assault or murder was still committed. Take a look at this
being applied IRL, for example.
As for the warning, you don't have any way of seeing if someone else is warned, and the staff member has no obligation to prove it to you. I must admit, he should have probably TP'd to you and explained it rather than using our remove option (the only way is by marking as spam), but that's not worth anything with regards to 'abuse'.
DENIED