When and how should internet service providers be allowed to treat some kinds of internet traffic different from others?

When the content of the internet traffic is deemed unlawful the internet service provider can discriminate,  block or slow down the internet traffic

Explanation:

The internet service providers have the right to block website that promote terrorists views or are used for recruitment by terrorists as well as other materials that are objectionable

The internet service providers can also discriminate against materials that are obscene, lascivious, indicate harassment, contains severe or exceptionally high violence based on preparation of materials to be published through them on the internet, according to a 1996 federal law

Internet service providers can also provide as zero rating sites that are exempted from requiring data allowance so that they can then be viewed for free by the client.

(because i need 20 chars)