And you might be right. Given how the majority of the folks were positioned, backs flat to the wall, might obviate the notion of "physical obstruction". Also, simply the singing of hymn too might remove intimidation. They may have had knowledge of FACE and how it applied. Were they sophisticated enough to be "just" legally outside the elements provided in the statue? Possibly. That ultimately will be for a jury to decide. But based on the link Conor provided, and previous cases under FACE these guys will likely get a fine and probation - assuming this was first offense. I don't know what they've been up to before, so I can't say for sure.
I guess the more important question you posed - is there " a need" for this service? But that's a question for another day. I was more interested in Conor's take on a legal argument that could be made. Not the moral question of abortion.