They arent mature enough to handle other opinions because it is almost entirely baseless. Most of the propaganda for anti-aborion is just calling people murderers and shoving pictures of disembered fetuses in their face. I don't trust a cause that relies on shock value to spread their view. I have never seen a pro-choice protestor holding up disgusting signs.
Still, this protest was entirely legal, and is one of the more peaceful ones from the sound of it. Unless it became a lot more disruptive this is fully protected by the first amendment.