Why do some converts become harsh and judgmental about the rules?

I asked the bishop about this trap of hypercorrectness, where converts become zealous without discernment and even judge people who don't do things the way they think Orthodoxy should be done. He told me the spirit he grew up with in Simonopetra was not one that encouraged monks correcting other monks. If they saw something wrong, they would mention it to the elder only, because if a brother needed spiritual help, the elder needed to know.

But they would not go directly and correct someone. It was not their job. We don't know what the other person goes through. We might see something that doesn't look right, but we don't know the pain in the other person or what they can handle. His elder was very big on knowing our limits, and not just physical limits: emotional, psychological, and spiritual limits.

He gave the example: I can't run a marathon, and if I tried, that would be lack of discernment. And if someone corrects me that I don't run correctly, what am I going to do? I do what I can. That's my best. The rules are there to facilitate the person's connection with God. They are not the goal in and of themselves. He told a story: a man was given 20 rules by a spiritual father and fell into despair, unable to do them.

Another spiritual father told him, just keep your nous, your focus, on God, and see how you go. Time passed, and when he looked back, without trying he had fulfilled all 20 things. The Sabbath is for man, not man for the Sabbath. The law is there to help, not to replace God. Of course, without rules there is anarchy, but we keep them according to our strength, in cooperation with our spiritual father.