No.

If Parler was deemed illegal (eg: it was ruled by law that it's facilitating terrorism), then YES.

If they are violating Amazon Terms of Service / Apple's Terms of Service, then YES (TOS is a bit of a grey area, but assuming that things are clear enough, those should be enforced). One can argue about a monopolic market position, at which case it's the role of the Government to solve the issue and regulate (in a theoretically speaking, well functioning capitalistic framework).