When you assume the worst in people, that is exactly what you’ll get. Perhaps the POTA operator couldn’t hear you or the conditions are different where they are. I just spin the VFO and move to another frequency or change band. I also choose to not operate on contest or special event days when the bands are packed. Only you can control your feelings and reactions towards stuff like this.
All that said, I have noticed a very competitive feel towards POTA operations. Specifically, hunters sending their call sign at high power before the OP calls QRZ. That is a concern for me since I subscribe to the “Use the minimum power needed” ideal and typically send 5W. I can’t and don’t want to compete with the folks running 1000+ watts. I just choose not to try and break in and move on.
Remember that how you respond is your choice.