To argue a counterpoint, why do you think they regret it now? Perhaps because there's a wave of people wringing their hands and saying "Oh my goodness what did you DO to that poor child?"
Here's a little secret: parents (at least the ones who are worthy of the title) live in constant mortal fear of fucking up their kids' lives. We have to make decisions on behalf of our children each and every day, and we lie awake at night hoping that they won't end up in therapy in their twenties (or dead) because of a well-intentioned choice we make today. And we have a constant chorus of people on either side of any issue, preaching and berating.
How could you vaccinate??! You could have given them autism!
How could you not vaccinate??! They could get tuberculosis!
How could you let them play with that??! They could injure themselves!
How could you forbid them from playing with that??! That could damage their self-esteem!
How could you let them watch TV??! It'll damage their brains!
How could you forbid any and all TV??! Do you want their lives to be completely devoid of fun??
How could you feed them anything that isn't organic and homemade? You know what they put in that stuff!
How could you deny them Jello? I mean...it's JELLO!
We've heard it all, from all corners. And we finally agreed that we will consider the pros and cons of the various topics, and after we come to an agreement, everyone else on the planet can kindly go fuck themselves vis-a-vis that child-rearing topic. That includes mother-in-laws, well-intentioned friends, child "experts", etc.
We came to an agreement on circumcision. Thus....