Mat 23:27 “Woe to you, scribes and Pharisees, hypocrites! For you are like whitewashed tombs which indeed appear beautiful outwardly, but inside are full of dead men’s bones and all uncleanness.
28 Even so you also outwardly appear righteous to men, but inside you are full of hypocrisy and lawlessness.

The scribes and Pharisees were the perfect example of this standard. They held themselves to their own outwardly standards that they had made for themselves (on top of the law given by Moses), only in part to the actual law and when noone was looking, to a different standard.

This is the standard that a lot of people are used to seeing in religious people, including professing Christians. Instead of the one seen in the world where the outside of the article is grey to black and the inside is something similar, they see a beautiful whitewash on top of something that isn't necessarily any better than the content of a grave. Whitewash on dark grey or black, for short.

The one thing that whitewash is not, is transparent. There is a slab of stone between the whitewash and the bones found in the actual grave. If it had been transparant all the way through then the inside would have been visible rather than the exterior. Some of the people of this world are fairly transparent and the grey or black shows. Some are not particularly but there isn't necessarily a large mismatch between the exterior and the interior.

Can they tell the true interior with religious people ? Often they can and mostly they can at least to some degree. If the exterior is too non-transparent then that is a sign that the interior is very different. If the nice looking exterior is too non-human then it doesn't match the interior because there is no way that the interior can be non-human.

True holiness causes problems. First, there is a level of transparency. Not because the person is trying to be overly honest or doesn't care or something like that but because the person can afford to be somewhat transparent. He might even want you to see through to the interior because that is where the Holy Spirit and a new nature in the likeness of Christ dwells. Second, the exterior isn't non-human. Just because it is different to the usual shades of grey to black that the people of this world display doesn't mean that it is non-human. It just means that it is in a different shade.

Even when people figure this out and see the exterior and the interior for pretty much what it is, it may still cause problems. Even persecution. I remember being on a bus somewhere in Africa where most of the people that weren't already Christians had been saved during the last couple of hours. There were a couple of characters there, probably part time criminals, who got very upset about this. Especially since they couldn't figure the man behind this unusual scene for some kind of whitewashed tomb. Or that was my impression. They got very threatening and I'm quite sure that the only reason why they didn't attack us physically was because a few of the new converts took a stand against them and that amounted to too much trouble for them.

Why can it cause even persecution ? Because people are used to being able to control their surroundings and thereby their own perception of the world around them. They are used to being able to figure out the interior for some kind of shade of grey to black and at the same time why the exterior looks the way it does. Being unable to do that can be very upsetting. In the case mentioned the characters were probably looking for a reason to dismiss the whole scene as a bout of religious hysteria, thereby excluding themselves from the whole thing as mere observers. Being unable to do that made them aggressive because they lost control of the situation.

The same scribes and Pharisees, the ones that didn't have a change of heart that is, lost control in relation to Jesus. His miracles were too convincing, his teachings were too convincing "never has a man spoken like this man has spoken", the man himself was too convincing. So they had two choices, to have a change of heart and let their perception of the world around them change. Or to release Barabbas and have Jesus crucified instead. They made the latter decision and it was a sad day. Let's hope some of them had a change of heart after the resurrection when his disciples demonstrated the gospel in Spirit and power once again.