> criticizing the "stuff" is okay ... but not the "person"

In my experience, people generally cannot tell the difference.

Often/Usually

It's possible that I'm at fault in my approach, though.

Probably usually not. Broadcasting good intentions only gets you so far. For most of us it's high skill communication. Earned trust can pave past issues. Past that it's often a minefield of psych factors (you+them) - like having a good/bad day, internal disciplines, where is self-esteem in the equation. A good read on the other person can make mines visible.