Yeah but a lot of people who are currently pretending to be straight or even homophobic might actually be closeted themselves or they may have some real dirt on them.

Your boss won't fire you for being gay if it turns out that they themselves are closeted or if they are laundering money, avoiding taxes or doing drugs, etc... Or even if your boss is in fact a very simple perfectly-behaved person, then 90% of employees in the company will have something potentially embarrassing about them and they're not going to fire 90% of the company.

The higher you go up the ranks of society, the more dirt you will find.

And the beauty of it is that people who are higher up the ranks will be uncovered first (due to public demand). The researchers didn't go after just anybody, they specifically looked up a politician and a judge. These are the natural targets; people who are supposed to represent and uphold society's moral ideals.