We all shun. We just do it for personal reasons. You don't like someone, you avoid them. Someone wronged you, or lied about you, you avoid them. It's a choice we make, based on our experiences with that person.
The WTS takes this to a group level. You're in the club, but break the rules. Now you're no longer in the club. The other club members are told you're out, and they collectively shun you. True, it's not based on personal interaction with you, it's based on obedience to the leadership, and compliance with the collective, but break it all the way down, there's nothing you can do about it. Like so many said already, you can't make someone talk to you, or accept you. By not adhering to their rules and traditions, you put yourself in a position of possibly being shunned.
The terrible part of a religious group who practices shunning is how they coerce family members to shun their own family. It is a terrible thing, but even in the 'real' world there are people who have had to disown family members for various reasons. That was a personal decision, based on experiences and facts of dealing with that person. In the JW world, that decision is based on compliance with the WT leadership. No petitions, or laws, are going to change that.