The baptism for the dead only aids an applicant, it is not an enrollment. Nobody is admitted unless they ask for admission. Nobody is admitted against their will. Mormons do not believe that a baptism for the dead makes someone a mormon in the hereafter.

Mormons believe that when someone dies and realizes they are not entirely dead they may rethink some of their prior convictions, especially when the gospel is then preached to them in an entirely different set of circumstances than in mortality or for the first time (as in most cases). Mormons believe that in such circumstances some that did not previously want to be admitted will seek admission. If such a person actively seeks admission, then the baptism for the dead can benefit them. If they don't want to be admitted, the baptism for the dead is entirely meaningless and they will likely not even know it happened.

You are trying to add in an element of coercion where there is none. The mormons do not believe they can make you go to the play, they can only leave a ticket should you decide to come. The mormons do not believe they can make you do anything or make you into anything you do not want to become. A mormon baptism for the dead is just as coercive (and intrusive) as if someone had written your name on a piece of paper without your permission and kept it in her home.

And of course all of this has meaning only if the mormons are actually right. If mormonism is entirely fake, then the gospel will not be preached to the dead and the work for the dead done by mormons is totally meaningless. If it is meaningless then why be offended by efforts made in secret that you will never know about unless you try to find out? Would you be angry if you found out that a friend of a different faith said prayers on behalf of your soul.