> He claimed to me that Mac is not a supported target of Inkscape
Unless I see a direct quote, I'm likely to suspect that what he actually said was along the lines of "We do not have developers using macOS, so we barely support that platform. Would you like to help us?".
> ...and then blocked me
I don't really know you at all, but I know Martin a little. He can take a punch, so blocking someone means he had serious reasons to be annoyed. OTOH, I'd rather not take sides here, that's between you and him.