So, you are willing to suggest that 'most' attacks against abortion clinics come, in general, from the Right, yet you wish to quickly suggest that there is little if any chance that a crime against a church such as this has any Left-wing political motivation whatsoever. You're entirely welcome to your opinion of course, I'm just intrigued by your willingness to spell it out in it's glaring inconsistency.
This is all just conjecture, of course, but the evidence I'm seeing points to a bunch of drunken or drugged kids who have been getting a preponderance of Leftist, anti-religious messages in their lives and so when they're in a troublemaking mood their first impulse is to target the object of their derision, a symbol of tradition and religion.
Again, I will be delighted to post any public statements from Left-wing organizations who wish to disassociate themselves from this, but I won't hold my breath, as such statements have been historically sparse in such circumstances.