If you surround yourself with like minded people, you are more likely to accept the group view.  Parents typically hold a lot of sway over their children.  Religious schools, religious colleges, NRA,  political party membership, also fall into this category.

Ronald Regan before he married his second wife was a Democrat.  His second wife and more importantly a rich father in law influenced Regan to switch to become Republican.

Being a part of a like minded group can to some extent cement a person in place from reviewing the basis for their beliefs and looking at the facts from a fresh perspective.