I know two people that left the union last year directly because the Unions said it was going to fund a campaign for the ALP.... they were not give a choice. 

good riddance. people that arent prepared to contribute to the defence of their own jobs and entitlements should leave. after all, who else is going to help them. its somewhat parasitic behaviour though. there is a  word for it .

How is it different from politicians or local government candidates doorknocking or shoving leaflets in your letterbox, or Jehovah's Witnesses, or people going door to door with petitions? 

The union I was in asked by taking a vote.

They also asked for campaign donations.

It's not done by deception.

I know two people that left the union last year directly because the Unions said it was going to fund a campaign for the ALP.... they were not give a choice.

Yes, they were. They chose to leave the union.

I know two people that left the union last year directly because the Unions said it was going to fund a campaign for the ALP.... they were not give a choice.

Did they also refuse any pay or conditions improvements the union may have negotiated for them as well?

I was actually told how bad the unions were in the last negotiations..... but it is against the law to negotiate you own wage so they had no other legal option.