Then why didn't you make the point of asking him when you were there, since he would know better than anyone here as to why it's dangerous. Sorry, not the answer you wanted but, any answer you get here is just a guess. I know nothing of you case, or your doctor.....might have been some type of problem with the MRI machine and has nothing to do with you ?
MRI is quite safe and I don't know why he has declined for that investigation. He might not have felt it to go for MRI investigation, so just to avoid it he told it to be dangerous. It is quite safe. If you feel it necessary you can do that.