Agusta in Italy had quite a different view....when teaching on the Chinook there and "non-union", during the annual strikes Management told us to down tools and honor the strike.
But as Nick says....it is an individual choice.
For me....I have never crossed a picket line....except when in a management position at the facility being picketed but still dropped of the doughnuts or cinnamon rolls. Perhaps we were lucky in that despite the strike friendships remained intact.