Re: did they look at all for someone intending on causing mischief?
If you are looking at malicious actions then you don't need to look at C band 5G. The problem is with frequencies several hundred MHz away, and it has been claimed some aircraft's front end RF filters aren't good enough to reject that. If you are malicious you will broadcast directly on the frequency the aircraft are using, which obviously will cause them plenty of problems.
People broadcasting on whatever frequency they please will cause no end of problems, aviation is just the tip of the iceberg. That's why the FCC regulates who can broadcast what on what frequencies under what conditions and under what power limits, and prosecutes those who violate it. You can't protect against such malicious actions anymore than you can protect against someone deliberately crossing over the dividing line on a two lane highway to crash head on into you.