The real question is "Should people expressing a pro-life view be subjected to laws that people expressing pro-choice view are not?OK an interstate highway is a major road. Do you believe people have a right to express their "dissent" by shutting down interstate highways thus blocking other citizens from engaging in their private lawful business?
Do you believe citizens have a right to carry out their private lawful business without interference from other citizens even if those citizens are practicing their right to "dissent"?
The right to assembly is the right to "peacefully assemble", is mounting a protest, I mean a dissent, which shuts down commerce in the business district of a city "peaceful assembly"?
Is it consititutional to say that Pro-life people cannot demonstrate on a major highway because it would be "blocking other citizens from engaging in their private lawful business" and then turn around and say that it is ok for a pro-choice group to demonstrate on that same highway?
The point is that the ban on flag burning has everything to do with the emotionally charged content of the idea being expressed. If they banned the use of fire altogether it would be a different story.