The use of trademark enforcement to coerce conferences into certain policies (which might contradict local law) is a deal breaker. It also demonstrates a willingness of the foundation to use wield power for purposes completely unrelated to the language.
There is no such things about forcing policies for conferences in the current trademark policy. (You're getting confused with a proposal that is being re-worked)
And even if there was it's hardly a deal breaker to use the language.
The proposed policy, which is clearly political in nature, has resulted in our firm decision not to adopt the crab language for our projects. Although Rust™ offers valuable features, introducing politics into the equation was both unnecessary and has caused a rift that may prove difficult to mend.
I just wish their trademark policy relaxed some of the non-trademark related requirements making it a deal-breaker.