I have this idea that if Jehovah's Witnesses were subjected to the same treatment as during the Nazi era, they would not be as resilient as the witnesses then. The reason is because the reliance on the individuals conscience was allowed more during the 1930's-40's than is allowed today. They had a sense they were taking a stand themselves by their own volition where today the laws of the organization prescribe the smallest minutia, resulting in robotic followers. When confronted with real horror and the difficult choices of survival, today's witnesses would only then start to deeply think about their religion and its implications.
Also in Germany only about 7000 witnesses entered into the camp system. These were the actively preaching witnesses who were arrested. About 15000 witnesses became inactive between 1933 and 1935 due to the Nazi ban and were therefore essentially left alone. So you ended up with the most devout witnesses in the camp system, hence their steadfast stand. If it were to happen today I would expect that about 5 million of the current 8 million followers would sign a compromising document (using the German statistic as a guide).