I totally agree. But I also want to add that I don't think a persons beliefs should really matter, but rather their ability to not inflict their beliefs on others.
And it's not just about abortion, although you will have to accept that if you're in the medical field. Homosexuals, multiple partners, promiscuity, people doing all sorts of things that are "bad" in the eyes of religion. Do you think you can help a 14 year old with birth control? Explain how to use a condom correctly to a gay teenage boy? Treat a woman who's had multiple abortions and multiple partners, but has no interest in changing her life? And can you do it all without judging and providing supportive care?
People are cautioning you against a medical career because they, like me, don't EVER want to be subject to someone else's personal beliefs when it comes to my body and my health, and you have made it very clear you have strong personal beliefs, and if you CAN'T 100% put them aside for a career, you will be bad at a job in medicine.
We all have to face that there are some things we like or are interested in that just aren't a good fit for us. This might be one of those things for you.