Now if they were subject to the same laws that traditional media is then I would agree with you on your first point, but then again these companies would never have been able to grow to their current size if they were.
As to your second point, the party is not calling these views republican. It is however stating that their views, no matter how repulsive, deserve an equal opportunity to express themselves in the public square under the first amendment.....and the fact is that these platforms have become the public square..... Jack Dorsey admitted to that during the congressional hearings and safe harbor strengthens that argument. Now if they want to use the private company excuse that's fine, but then lets strip out the safe harbor provisions since they are not acting as neutral parties.
But if you maintain a whitelist of people through some manual approval step (such as a blue checkmark) I could see that being a different matter.
Traditionally though that meant abusing as in (1) deliberately consuming disproportionate resources or (2) attemtping to undermine the infrastructure. Not in posting things that are considered by leadership to be bad.