There are a lot of variables you are ignoring here. And I don't know why you're so mad, i wasn't talking about you specifically but speaking generally about the recommendations thrown here.
If your car made those noises at thinner viscosities especially the ones recommended by engine manufacturers then the most likely explanation is your car engine has issues, most likely wear and tear. It can happen even on low mileage cars if the owner doesn't do such a good job of maintaining it. In that case, YES, you will need high viscosity oil to coat the parts.
You cannot just go on recommending what oil worked best for your car for everyone, your car might have wear and tear but others might be maintained well and such a drastic oil change will not be good for their engines. You want the oil to get in the moving parts and coat it, too thick and it can't flow there, too thin and it's not coating properly.
Now get this, if you use a thick oil from the very beginning you're damaging your engine to the point soon you will have no choice but to use thicker oil. Newer modern engines have intricate parts woth tight spaces, older engines have so much wear and tear that even thick oil can flow better in there.
Now most owners manuals recommend several oil grades. If its a new engine use the thinnest recommended according to the weather you have. As the engine ages, move to a thicker.
You're right, at 100000+kms you need thicker oil.
As far as dust etc is concerned, that's the job of your oil filter. Get a really good one and change it often.
The choice is pretty simple. Follow your car's manual. If you bought the car from someone else, use what the old owner put in.