HR is a funny one; if you know what you're talking about about and can speak to different audiences at their level it's not generally push back from a professional knowledge point--pushback for HR is usually "yeah but that is hard/not what I want" which is very different and totally fine.

Except fucking compensation. Glassdoor is the WebMD bane of comp conversations with employees. It's a selection-bias informed group of people who provide salaries when they think they're underpaid and need validation. While, for the most part we're all underpaid, just like WebMD, the dangerous oversimplification of very nuanced and complex data is nothing but a PITA to people trying to to fix or work in good systems.

"I saw my job is being hired for $xx,xxx I should be getting that". Location, industry, industry segment, education, KSA, org size, high variance in titles from one company to the next(manager here is VP there), every other pay/bonus/benefit/time off difference, internal pay equity considerations that are often statutory by state/feds--none is captured and people aren't taught that those are part of comp. Just this title is $xx,xxx. The worst part is that managers run to HR with often this info directly supplied by candidates or their own employees all worked up HR is fucking them by underpaying. I'm the first person to tell a manager their comp is fucked against a market if it is, which helps build trust but it's exhausting.

This plays out in every job offer, promotion, annual merit increase and any time you remind people they're not coming to work for free.

Again, almost never see this in other areas if you know what the hell you're doing in HR, but I guess the incentive and stakes are high enough in comp to make people just go off the deep end.