Probably should have considered that before you ".. had a civil but slightly tense conversation with an friendly-acquaintance Manager X at my local upscale national grocery store over what I considered over-exaggerated risk-prevention measures over Covid19." That was probably NOT the time or the place to have such a discussion with a "friendly acquaintance" because that "slightly tense conversation" made it higher up to management and HR such that you tainted yourself. In the end, it seems like you had an out of place discussion with someone you don't really know in a place that isn't their to make friendships where opinions such as yours can be expressed with no consequences.
You failed to realize that you probably made the manager and other customers/employees uncomfortable AND that this policy probably wasn't set by that manager based on YOUR beliefs and you tried to sway his/hers at a time where they had more important things to deal with...
you burnt that bridge royally for many reasons. And no there is no requirement that once the interviewer associatd that conversation with this interview that they had to continue on...nothing you did/stated was protected.

