Yes, it's a losing argument to blame the WTS for shunning.
First of all, they can't really shun you. Is the Governing Body that never spoke to you not going to speak to you? Only your friends and family can shun you, people that you care about.
So put it on them, don't give them an "easy out". If they can blame the WTS and if you also blame the WTS ... well you've agreed with them that they have to and can. Instead, tell them that they don't have to, that the WTS has no power. That it is completely up to them what they do ... and you'll judge them for it.
Don't reenforce the belief that the WTS is in control and the people have to do what the WTS tells them. Remove that thought, introduce the idea that they can chose what to do.