There is a standard and they are held to it. It is the Constitution.
"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people PEACEABLY to assemble, and to petition the Government for a redress of grievances."
Correct me if I'm wrong but neither Twitter nor Amazon can pass legislation. Parler can buy it's own servers. No one is using force to deny their ability to spread hate. They are simply inconvenienced. Freedom of Speech does not equal Freedom to Lie.
A police officer was murdered. A mob tried to over turn an election by FORCE. A free and fair election is a form of free speech. Let us be clear who is stifling free speech. It is the Mob.