In this case Parler already had a policy in place that banned posts calling for violence / anything else the breaks US law as well as report buttons in place to report it (Reddit and Twitter use similar systems), but there has been enough gaslighting in the media that voted "yes" in this poll never even bothered to look at their ToS prior to voting.

You can post ANYTHING YOU WANT that's awful on Reddit or Twitter, then immediately screenshot it before it can be reported / cleaned by mods and scream "They allow hate speeeeech!" like they've done to Parler.

The companies made a choice based on their political views, not based on public safety / ToS violations and THAT is why have centralized duopolies on social media is so dangerous in the USA.