2) Twitter isn't a post office, it's a privately owned website. They do not handle transportation requests for information on the internet, just their own private servers meaning they are not a common carrier.
3) Even if you conflate twitter with being a privately own post office, CC laws do not prevent them from putting "Toxic" stickers on any toxic waste being handled by them.
Would it be acceptable to you if your ISP inserted warnings for emails you sent? I understand we have "spam" classifications but this goes beyond that and is done client-side and I can modify my client to not mark messages as spam. Would you consider the addition of a warning to all emails you sent a modification of your message?
Your point of "toxic" labelling is interesting. I think there is a difference in the non-physical realm though as "toxic" as it applies to ideas is subjective.
It wouldn't be acceptable to me but ISPs aren't regulated in that way and have attempted to use the argument that requiring them to carry information without any modification/discrimination is a violation of the ISPs free speech rights.
It's weird how the administration that is responsible for de-regulating ISPs also wants to regulate platform-holders because they're concerned about how they treat their message.
We don't need to go far to the conclusion of that line of questioning: Twitter actively deletes spam accounts and takes measures to block troll factories from using their platform, and this is not controversial.
2) Twitter isn't a post office, it's a privately owned website. They do not handle transportation requests for information on the internet, just their own private servers meaning they are not a common carrier.
3) Even if you conflate twitter with being a privately own post office, CC laws do not prevent them from putting "Toxic" stickers on any toxic waste being handled by them.