Compelled to speculate on what though?
I don't know what bit of my description of their behaviour made you think they might be changing people's minds for any other reason than that they managed to frighten and intimidate some woman away from the clinic.
Which is not really changing someone's mind, it's bullying them to go through with a pregnancy they do not really want to continue. Or delaying a termination for a week or two more.
I've seen them in action and never once thought they were doing anything that could reasonably change a woman's mind. They are doing things to frighten women, and upset women, and to make women feel guilty, and to distress women, and to intimidate women. But nothing to help women.
And as Giles said, even if they did manage to make someone change their mind, they still haven't changed their circumstances. What they are doing doesn't suddenly mean that a woman is emotionally or physically more able to continue a pregnancy, or make her relationship a safe one, or her finances more stable, or her baby more likely to survive if she's terminating for medical reasons, or change any of the thousands of other reasons which led to the woman making her own decision to terminate in the first place.
Also they are sending a message out to women who are not even using the clinic and it's services. Telling them that this is what they will face if they ever are in need of the clinic. Intimidating them in advance.
That's not changing people's minds, it's controlling them through fear.
They know nothing at all about the women using the clinic, or the women just walking down the road, yet they feel they can block their path and sing their songs and force their pictures at women and shout their slogans and demands at them.
And then they walk away with no real idea or no real care of what they've done to people that day, what pain and upset they might have caused, but they still come back again a week later to do it all again.
So no, what they are doing, what I've seen them doing, what they've done to me, it's never made me speculate on anything regarding them changing women's minds, but it has made me very certain that they are harming women and frightening women at a time when they need support, not guilt trips and harassment.