Adding onto your point, I was raised as a Jehovah's Witness and I would like to make it very clear that members of the congregation are only disfellowshipped after:

• The sin has come to light.

• The elders and others in the congregation have tried to help them correct their course of action, this always involves multiple counselling sessions, and multiple offers of assistance.

• They are unrepentant and will not accept counsel or help.

The last point is why people get disfellowshipped. They are doing something very wrong, they have been made aware of that, and through pride or whatever else they refuse to change their behaviour or accept help. A Jehovah's Witness could in a fit of passion murder somebody. It's highly unlikely, but let's use it as an example. If they were open and remorseful about it, accepted counselling from the elders (who would likely take them in to the authorities themselves and provide counselling), they would not be disfellowshipped, and they would be provided with regular visits/spiritual and material help whilst in jail if that was the outcome.

Unfortunately the major cause of disfellowshipping is adultery. Many people who are found out for cheating on their spouses are simply unrepentant and won't break off the 'relationship'. They are content to break up homes and bring dishonour on not only the congregation, their families, but also Jehovah's name. Any reasonable person can see that that kind of behaviour cannot be tolerated. The elders are sheperds. They are there to serve and protect the congregation. If there is a sick sheep, the sheperd will quarantine it and treat it before the rest of the flock is infected. It's the same principle.

Once again, this type of extreme action is taken ONLY after the person concerned refuses to change. Can you imagine having an unrepentant adulterer attending the services whilst their family and the other people affected have to stand by and watch? No reasonable person would countenance that.

Reddit makes a big deal out of 'shunning' as it's familiarly known. Just bear in mind, everyone shunned gave their oath in front of God, and they broke it, they did something really bad whilst full well that it was wrong.
When offered help, they decided to go their own way. Their own pride and stubbornness got them disfellowshipped, nothing else.

The door is always open for people to return to the faith, and they're given assistance to do so. I speak from experience as my brother was disfellowshipped. It wasn't easy on our family. However, he humbled himself, he accepted that his course of behaviour was wrong, and it's as if it never happened. It's not something people hold over your head or punish you with, sometimes though it's necessary discipline and is done only with the good of all concerned in mind.