“whatever reason Amazon gave” was dismissive, but also accurate. They gave a reason. The poster dismissed it and the comment was downvoted for the dismissal.
You don't know why it was downvoted; the comment just wasn't very helpful at explaining or clear (I didn't downvote). If the reason was "unpaid bill" that would come under "whatever reason" but would that be relevant to policing anything?
Without knowing what reason Amazon gave that leaves me to go look it up; I do, and see various news site quotes including "District Judge Barbara Rothstein sided with Amazon, which argued that Parler would not take down posts threatening public safety." quote on npr.org, and "Amazon told Parler it would boot the company from its web-hosting service [...] because of repeated violations of Amazon's rules" on NYTimes.com, I try to find an official looking source of exactly what reasons Amazon gave and get to the filing for the lawsuit/legal case between Parler and Amazon[1] which includes on page 3 "17. During this same time period, AWS claims that it received reports that Parler was failing to moderate posts that encouraged and incited violence, in violation of the terms of the CSA and AWS’s Acceptable Use Policy (“AUP”). Exec. 2 Decl., ¶ 4; Ex. C (AUP). The AUP proscribes, among other things, “illegal, harmful, or offensive”". It's not clear here whether Amazon is claiming it was illegal or not, or whether it actually was illegal or not.
I google "inciting violence illegal usa" and get to a Cornell Law School[2] page on 18 U.S. Code § 2101 - Riots - saying, abridged, "whoever uses a facility of interstate commerce including but not limited to telegraph, telephone, radio, to incite a riot or promote or organize a riot, or aid or abet any person rioting or commiting any act of violence furthering a riot, shall be fined or imprisoned". Still not clear whether Parler was actually breaking the law or whether Amazon was alledging that they were, or whether this has been decided, or what exact reason Amazon gave.
I know there are arguments about whether hosts are or aren't responsible for content on them, or are just blind transmission systems, but I don't know which way it falls in which scenarios.
It reads more like a complaint about Parler being taken down than a helpful explanation, and could be more clearly and directly said "(policing legal content) means a company removing things against their content policies, even if the things are legal" in as much space and effort.
Each action was ideological.