I guess the prevalence of such attacks would be an important thing to consider...
As another poster linked:
Since 1977 there have been eight murders, 17 attempted murders, 42 bombings, and 186 arsons targeted at abortion clinics and providers across the United States. In some cases, a small group of clinics have been targeted multiple times.
So, those are spanning a period of 45 years.
It's too early to tell which form (pro-choice extremism vs. pro-life extremism) is more pervasive or likely since the events being referred to in the OP are in response to a ruling that happened only weeks ago.
Now...
If a year from now, pro-choice extremist violence matches the kind of numbers it took pro-life extremists 45 years to rack up, then we can definitively say which side is worse (or more likely to act out in extreme ways), but as of right now, it's too early to tell.
The part of this I am perplexed by, is why this lashing out is happening in California (a state that has no intention of restricting abortion rights).
An "abortion alternative" facility in California is outnumbered by legal abortion clinics by a massive ratio, and poses no real threat to legal abortion in Cali.
It'd be like if there were radical pro-marijuana people (hypothetical obviously, I've never met a radical violent pro-marijuana activist lol) in a recreational legal marijuana state (where they already have the thing they want) choosing to vandalize the offices of a small, inconsequential, local organization that opposed it.
When the radical activism is "punching down" and not "punching up", it comes across as just trying to "make a statement" more than it does "fighting for a cause"