In my opinion it would be unwise to not recognize that everyone, including you and me, has vested interests. It’s just part of being human. Do we have vested interests in who we are voting for and why, where we live, what we do, who we hang out with and what we believe? Of course we do.
For instance, someone who believes all birth control is wrong will have vested interests in believing the pill causes abortions. Why? Because that will be another reason they can claim the pill is bad.
And someone who has used or prescribed the pill will naturally have strong vested interests in believing it does not cause abortions. Why? Because if you’re prolife, the last thing you want to believe is that your actions and advice may have resulted in the deaths of children.