"I do not understand what it is intended to mean. "   Maybe if the two passages are modified slightly:

'An individual whose "faith in god as the giver of life" brings him or her to believe that abortion is contrary to that faith has every right, under the law, to choose not to have one. He or she has no right, under the law, to deny anyone else" the right to have an abortion.'

'An individual whose "faith in god as the giver of life" brings him or her to believe that slavery is contrary to that faith has every right, under the law, to choose not to have one. He or she has no right, under the law, to deny anyone else" the right to own a slave.'

In the second case of course the law has been modified rather dramatically since a time when it was true. Which I take it was the point that bruce was making.