FWIW that pattern of behavior has little to do with "being a progressive" and instead reflects the cultural norm. I'd even go so far as to posit that "progressives" are more likely to point out that, no, there's really not "a racist" but a person can hold a lot of extremely racist beliefs - the same way btw as there's really not "a progressive" but a person can hold a lot of progressive beliefs. A system can be "racist" in that it can be built on and to uphold racist attitudes or beliefs but a person can't be "racist" because racism isn't an intrinsic and immutable characteristic (neither is "progressive", "Catholic", "criminal" or "Republican", to name a few examples explicitly).
But precisely because you can't actually be "a progressive" but merely hold some progressive beliefs and opinions a lot of "progressives" uphold the same harmfully essentialist views as "non-progressives" who balk at being called out for racist opinions, views or actions by insisting "I'm not racist" regardless of whether the accusation is "you're a racist" or "you said/did something racist".
"Felon" is an obviously silly example as it's just a more specific form of "convict", i.e. someone convicted of a felony crime. It's often used in an essentialist way (but of course selectively so) but the more obvious example would be "criminal" because it is often used in a way that suggests an intrinsic essence of "criminality" even in the absence of sufficient evidence to make a legal case that would result in a conviction - or even the presence of an arguable crime at all. "Criminal" is thus distinct from "convict" in that a conviction is neither necessary nor sufficient for that label to be applied.
Back when I was a libertarian they were pretty big on this argument, not progressives, as libertarians were the open borders people and progressives were off on some other cause.