Many of those people view birth control as murdering babies since it prevents conception, and the only reason to be having sex is for conception. They see it as the same as morning after pill or actual abortion procedures, because all of it is about stopping conception). Talking to them, it quickly becomes very clear it is not actually about preserving the sanctity of life at all, but rather trying to force their beliefs about sexuality on others. They also justify it by claiming that the rest of society is forcing its sexual beliefs onto people (via porn or even just shows of affection, LGBTQ support, etc), so they think they're actually unshackling people from it. Its just more blatant hypocrisy and ignorance, and those people belief they are the absolute authority on it, or rather acting on the absolute authority. Doctors, government, any Earthly entity doesn't matter, this is coming from a higher power. Nevermind their whole spiel about God/Jesus being the only one that can judge.
Yup, as I've said many times no one actually believes that birth control or the prevention of conception is actually the murder of babies. They may lie to you (and to themselves!) and claim that they believe this but nobody actually does. It is entirely because they wish to force their own beliefs on sexuality on others. You are 100% right.