I agree with you in that companies should be left alone to do business the way they want to, within legal limitations. But, to echo what DeAnn Campbell has said in response here, the size of Amazon (and contextually the size of the third-party sales on its platform, which is much larger than the other marketplace-vendor sites) creates a unique consideration -- is there a point in market share where a company has to be "reined in"?
For example, in the EU now there are laws recognising that many small businesses depend on online marketplaces for their survival -- as such it is now illegal for Amazon to arbitrarily terminate third-party seller accounts and if they do so they can, upon challenge and judgement by the courts, be forced to resume business with the account or pay compensation, almost like severance, to the account holder. This same law applies to eBay and other sites in the EU.
Saying this, Amazon will likely increase third-party seller fees if they are forced to comply with this US bill, if it becomes law. In the UK there is a "digital services tax" levied on multinational corps supplying digital services in the UK. It's 2% of revenue I think. Amazon increased seller fees on the Amazon UK site by 2%, for example from 15% to 15.3%. Unfortunately many third-party sellers do not realise that they need to pass this on to the end user if they really want Amazon to feel the punch the government intended it to take.