Maybe I'm just a cynic, but this seems very much part of the PR script for any controversy of the past 20 years or so.
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Cause controversy
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Get backlash
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Say there were death threats in basklash
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Paint opposition in bad light, claim to be the real victim and bask in all the feel good comments from people saying "it was controversial, but come on, death threats are not cool"
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Conversation derailed, continue as planned
Seriously, go look at one of the comment threads on that other site. It's now all about how "deranged indie devs" are hurting honest hard working Unity employees. Maybe it was a real threat, maybe it wasn't, but they're sure as fuck going to milk it for all they can now.