Yes, generally people side with their family and loved ones over principles. My fathers family had their house aerial bombed by the french, so a few tram bombs just sounds par for the course of an independence uprising. But your main point is correct - violence is always ugly, and we have to be careful when rationalizing it to achieve pragmatic goals.
We can also generalize beyond our families, and make it one of our principles not to harm innocent people. This puts random bombings of trams or housing off-limits. How likely is it that these acts will achieve pragmatic goals anyway?
Well, when one group disenfranchises you via military conquest without such a Noble Distinction, and you cannot defeat them in a Noble Battle, you expand the available choices. And it seems to have worked out for most independence movements.
I'm not familiar with how it worked out with the Algerians, and whether attacks on civilians were a deciding factor. Of course, similar situations still occur today, when you have a colonising power with overwhelming military superiority, and the dispossessed resort to attacks on civilians.
