Earlier quoted context omitted.
Or it forces oppressive regimes to realize that they are being an oppressive regime. Want to censor the internet, fine, send your citizens back to the dark ages; see how long it is until they protest or move.
Amazon isn't in the business of forcing oppressive regimes to realize they are oppressive regimes, they are in the business of selling goods and services regardless of the oppressiveness of the regime governing the region where the currency comes from. If you want Amazon to stop doing business with oppressive regimes, contact your politicians about sanctions.
And if the solution was to force Amazon to block any access from their servers to those oppressive regimes, that wouldn't help Signal at all, because they too would be blocked.