This wasn't a peaceful protest so the amendment doesn't apply.

- blocking the only entry/exit point for other people who have places to go. Some of these are emergencies. What if you block an ambulance and indirectly kill the patient?

- creating a risk someone will hit you and be injured/killed/traumatized or even start a pile-up

It violates the rights of other people to free movement and causes them economic damages. It may also lead to catastrophic consequences if emergency vehicles are blocked (happened many times) and since the highway is a common property, regulated by the laws of the jurisdiction owning it, assembling there contrary to these laws is also a violation of property rights.

If I set up a "protest" tent in the middle of your driveway, not letting you exit the house, would you say it's a constitutionally protected activity or would you call the police on me, claiming property rights and trespassing violation?