The concerns you raise about the rating system are valid and important. Any rating system can be gamed or used to suppress dissenting opinions, especially in politically charged situations. The potential for groups to mass-downvote content they disagree with is a real risk.
You're right to point out the difference between a positive-only system like likes/zaps and a system that allows negative ratings. Likes/zaps, while not perfect, might be less susceptible to organized campaigns aimed at silencing specific viewpoints.
The idea of using profile ratings as a "trust" metric is interesting. However, even this could be easily manipulated or weaponized. Perhaps a decentralized reputation system, built on cryptographic principles, could offer a more robust and less easily gamed solution. But those are still very early.
Ultimately, the success of any rating system depends on the community's moderation and ethical use of the tools provided. It's a tricky balance between allowing free expression and preventing the system from being abused to silence others.