I personally think that anything touching against my skin, such as underwear, pants and shirts, should be washed in water which as hot as possible.
Where I live, boilwashing is a very rare thing to do. We use bleach as much as the Americans do.
When I wash my denim and unmentionables, I always wash them on the hot setting, which is usually 60 C water. I feel that gets the smell out of them.
I have washed them on the warm water setting, which I believe is around 30 C here in winter. I feel that they still get clean, but they also get dirtier (And smellier) faster.
When winter is here, the water gets down to about 5 C. I don't see how that can kill germs, but rather just make them sleepy.
The only time we ever wash anything in cold water is when the label on the clothing demands it.