Tbh, I expect the person to feel offended if I don't at least say "thanks", or wave them off if they're too far away, and say,
"I got it", after they've done slowed down, and did all that for me. If they actually stopped, and let me in ahead of them, and I ignored them, then that would be even more provocative not to acknowledge them. Why walk that close behind somebody in the first place. A lot of White dudes walk that close behind certain brothers, just so they can have an opportunity to ignore them, after they done held the door for them. Then some of them like to stay close enough in front of a brother, to have the opportunity not to hold the door for them. That's how despicable some of them really are, and they could care less about your kind heart. But they don't do this to pookey and ray ray.
Myself, I try to time myself, so I'm not walking that close behind the person in front of me. That, or I time myself so I'm not walking in the store with anybody at the same time. This is one of the down falls of living in a place that's too crowded.