The thing about a word like "parasite" is that it doesn't matter how reasonable or appropriate it is as a word to use in these specific circumstances, because it comes with political and historical baggage that we just can't wish away. It is exactly a Katie Hopkins kind of word, deployed against refugees, etc, and it doesn't matter a jot that Sheila Jeffries used it in a completely different, justified context, about a completely different set of people (and ones with considerable privilege, unlike refugees, etc). It doesn't matter a jot if we use a dogwhistle word not knowing that it's a dogwhistle word, or not meaning it as a dogwhistle word, because it will be heard as a dogwhistle word, regardless.
For example, while there might be legitimate, non-controversial, totally appropriate uses of the phrases "rivers of blood" or "all lives matter" in some contexts, I would never ever use them in a political speech, even if the political speech was about actual blood-rivers or actual mattering-lives, and even though my intentions would be absolutely anti-racist, not pro-racist. I would avoid those phrases because those two phrases also have considerable political and historical baggage, and those dogwhistles would be heard, even if using them as dogwhistles was as far from my mind as it could possibly be.
Is this self-censoring? Possibly. But it's also sensible, if we want to be heard. It's also sensible to understand why there might be backlash if I did use those phrases, just as there's been backlash here.