The real issue is that if a person no longer believes that the Watchtower is God's sole channel of communication on earth, they must be required to say goodbye to all of their family and friends if they wish to exercise this freedom of thought. The public and the legal system is mostly unaware of this and this is the whipping stick the WT seeks to protect with this action.
The only freedom you have is freedom to make your own choices. What you don't have is the freedom to impose your choices on others. Just as you were free to chose to be a JW, you're also free to chose not to be one. Your friends and relatives are free to chose to remain and to follow the suggestion to shun you or to not do so. It often comes down to how much of a zealot they are - the standard is mostly self-imposed.
The WT is free, as a religion, to suggest all manner of crazy stupid ideas. Most people have the same freedom to push half baked investment schemes, quack science and all manner of things that cause people ills. And those people have the freedom to believe it and follow it or not.
What no one has ever come up with is something meaningful that could curtail the WTS behavior which wouldn't itself be far, far worse than anything the WTS ever has or could do.
The fact is, people can and do leave. Not everyone shuns. Not everyone is "otherwise nice if it weren't for the WTS". The people who shun you often want to shun you - they are JWs because they get to be judgemental unloving pricks. THEY are the only people who can shun you.