“I have read that people assigned to this duty must be rotated out after a few months or they get sucked into the evil pit”
I was thinking something like that too. But if the guy is gay (don’t know either way in this case), they cannot be allowed near that work. Beyond that, hard to screen out people who might be vulnerable, beyond the usual means. Best thing to do is watch them very closely both inside and outside of work. I’ve always thought that if your job involves sensitive work, you should have the option of taking it with higher pay, but no privacy at all (even at home), or not taking it in the first place (not just these people, but others with Top Secret, etc.). If that’s done, then a person’s lifestyle can be watched and if something looks funny - like buying a mansion in VA on $100k a year, that can immediately be investigated - rather than waiting until all our Soviet assets are dead (which happened).
Remember though, Jerry Sandusky was married to a woman all those years, so even having a guy being married is no guarantee.