You seem to suggest un-professionalism is a Union based phenomenon.
No, not at all. I did experience unprofessionalism with some NZALPA staff over the Ansett dispute, but my own union - BALPA - is extremely professional and very measured in their approach. They believe in negotiation, rather than threats and intimidation. Sadly, I think the NZ union is about 20 years behind the times.
The REALLY unprofessional ones are the pilots that take advantage of industrial disputes to feather their own nests. They effectively undermine the unions, and can remove the element of negotiation from the dispute. Ansett NZ were very, very keen to break the strike by importing pilots from overseas - I think it is to the credit of the pilots they contacted that few, if any, took up employment.
You'll get unprofessional behaviour from both union and non-union people, when it comes to line flying. I don't believe that the conduct of pilots on the line has anything to do with union membership. People are people are people... some have a reasonable moral framework, others are entirely self-centred. In the airline I worked for in the UK, union membership was very high, and I'm sure that the reason was that the union was seen as measured and responsible. They certainly helped me out a few times, so I will always support them, and by implication their brother unions, of which NZALPA is one.
What I will never support is the idea that people who do not agree with the union line should be subjected to abuse, intimidation, violence or any combination thereof. It never changes anything, and it has the potential to wreck lives... but mostly, it is just thuggery. Not something that professional pilot should ever indulge in, regardless of what they may have been through.