Is Github owned and operated by a state or federal government agency? No? Then yes it probably applies. No person or business has to serve you, or buy from you, or employ you, or let you share their platform. It's their resources and therefor their choice to do so. If it were otherwise people might have recourse when Google shuts them out unilaterally, or when Paypal closes account for vague ToS violations.

Those freedoms enabled the best and worst behavior and let people make of it as they will. Laws usually concern themselves with the ways people abuse others: fraud, various kinds of violence, theft, breach of contract, etc. Regulations exist for industries where the risk of damage to many people exists: chemical waste disposal, lending laws, food labeling laws. If the industry needs regulation then that's what we should push for. My interpretation has always been that the constitution establishes what basic expectations of freedoms and restrictions we should have, and laws set the boundaries on where my freedom ends and yours begins.