First past the post is not the best system

If it is not offensive to someone to be reduced to a choice between just two parties then that person will never be in favour of pr. If people are fine with the two party system and see nothing wrong with it then you will never convince them of the benefits of pr because they are blind to the problems of fptp. You cannot make someone be annoyed by something... you cannot make someone see something. All that you can do is remove any other prejudices they may have and eventually they will see what you see.