You don't need to be vegan to care about animal rights.
I can consume closed-source software and care about FOSS at the same time, do not discard people who are on your side just because they aren't extreme enough for your tastes.
> You don't need to be vegan to care about animal rights.
Yes, but that's not really equivalent to this situation. This isn't just a "do you care about FOSS" question like the "do you care about animal rights" analogy that you raised.
In this situation, a person who pays for and uses closed source software (and not just one application, but the entire OS), is criticizing another company for making closed source software. It would be more equivalent to somebody who is a meat purchaser/eater criticizing a company for making meat.
I can consume closed-source software and care about FOSS at the same time, do not discard people who are on your side just because they aren't extreme enough for your tastes.