The only times I have had issues have been at discount stores, specifically Fred's and Big Lots, while checking out. And even then they weren't a huge deal to me. At a Big Lot's a few years ago, the SA held up the panties I was purchasing and said, "Panties huh?" I told her they were for my wife (one of them was) and she responded, "Yeah sure." I just left. Nowadays I'd make a scene but not then.
At a Fred's about two months ago, I was buying some stretch jeans and clearance panties. The SA asked me (while laughing), "Are these in your size?" I said, "Yes they are!" She laughed and told me to quit messing with her. For the first time ever, I was honest and tol her, "No really, they are." She just laughed like she didn't believe me. I went back about three weeks ago and bought more jeans from the same SA. No reaction this time, she was professional.