If an ISP were to agree to a proposition from Hasbro like that, then they would be required (by law) to publicly disclose that information, creating public backlash that would undoubtedly result in more consumer money shifting to their competitors than Hasbro could ever possibly hope to compete with.
The public backlash would only happen under specific circumstances. First, you have to be able to find the information. A public disclosure need only be public, it need not be easy to find. You would have to rely on a site like Open Secrets to find and publish that on the internet, which could be blocked by ISPs.
Second, the public would have to care. If you block Facebook or your favorite news site, yes, there will be backlash. The public won’t care about Hasbro shutting down our site. Plus, there would also people who actually support it as “free market forces,” which is itself incorrect because the free market assumes competition not the lack thereof.
As to them blocking a negative ad campaign, that would require basically shutting down every news/forum site on the internet, which for any ISP interested in staying in business is unlikely.
Although that is the simplest solution to blocking negative ads about your ISP, there are both technical and contractual ways around this.
0. You only have to block ad networks and shut down VPN traffic.
1. You write some tech to block ads that link to sites known to be critical of the ISPs practices. There are a few different ways I would go about creating this tech. The simplest being a browser extension that has a heartbeat to keep your internet on/fast. Now that you have a browser extension, you have access to ALL the web browsing content and you can do anything you want with each page; including blocking only specific ads.
2. Require all your customers to install a ROOT CA from the ISP. Now the ISP can read all your SSL traffic and decide what is censored and what is not.
3. The easier solution, block all ad networks unless they sign a contract that says they cannot publish ads that hurt the ISP. Or you give the ad networks a free fast lane if they comply. Carrot or stick works here.
When you let a monopoly ISP do whatever they want with the traffic and consumer, everything imaginable is on the table. Some are technically more difficult than others but nothing is impossible.