This is a terrible idea. It says that "you don't need to break the law to be punished". This give the big tech companies quasi judicial powers where the grounds for punishments are arbitrary and subjective. Only the courts should be able to decide this type of thing, and I hope Parler sues Apple, Google, and especially Amazon for billions of dollars.
What if tomorrow they decide to ban and de-platform an app with 5 million users because they didn't like the color scheme the app was using (or their rising stock price...)? It opens the dangerous door to anti-competitive behavior. Today it's Parler, and tomorrow it will be you. This is a double edged sword that will cut everyone besides the big tech companies. We must not allow this action to go unchallenged.