coffee addict,
This is word for word from the pamphlet “and it’s not just any mitzvah that you protested against. You have to know that the mitzvah of milah is one of only two mitzvos in the Torah for which you get kareis for not doing. It’s a very important mitzvas asei if he refuses to let himself be gemalt then he’s chayav kareis and hereyou were refusing it, you didn’t want any part of it
Honestly I have no idea what that last sentence means (it seems to be missing some important punctuation/words), but I’m pretty sure it doesn’t say that you get kareis for regretting having had a bris milah.