Because he thinks it makes him look cool and edgy, especially in an environment like this, where the way to gain popularity is to be the most extreme far left voice in the crowd.
People like that are the vegans of politics: even if you may agree with them in many ways, their repulsive attitude and conduct more than overrules any common views you might share.
Even longer than that.
But gas means money, so fuck anyone and everything else that might get in the way.