What do I think?
Don't ask
I think you should read around the subject as it has already been discussed.
BCUK's policy is that we do not condone illegal activities, and if you want somewhere to salve your concience about camping somewhere where you know you do not have permission, can I please suggest that this is not the place to do so.
My personal opinion is that if you choose to camp where you have no permission that is up to you; but if you are going to do so, it would be smarter, and less damaging to other folk, if you just got on with it and kept quiet. Endless discussion, without the addition of any fresh facts, is not beneficial, particularly when so many people seem to feel the need to crow about how their own beliefs outweigh the law. (not happened here, but it often does in this kind of thread)
I have heard, but have been unable to confirm, that if you were to be caught by police in an area where you had no right to camp, and were found to be carrying a sheath knife, saying that you were out "bushcrafting" would not help you much. The logic running that since you have no permission to be cutting vegitation, or lighting fires, you do not have a good reason to be carrying the tools to do so. I am fully aware that the police usually have a great many more useful duties than stopping green clad ramblers, but on busy days we often see a police car up on the Ashridge National Trust Estate. I have also seen one of the canine unit's cars parked up there, presumably so the officer could give his dog a walk. Just something to bear in mind.
It might also be worth bearing in mind that there are a lot of bush skills that can be practiced without camping out, or chopping wood, or building shelters. It often seems that when people get interested in bushcraft the "exciting" stuff like building shelters, having fires, using tools and sleeping out eclipses all the other, more subtle, but widely useful skills.