Spoiler: Some humans will never stop violating others until they are forced to.

Sitting around and waiting for the worst humans to build and control weaponry is retarded.

Explosives have mostly ended kenetic wars compared to what they used to be.

I'd rather blow up an enemy than keep sending in tens of thousands of my own people to just get killed.

Pacifists tend to live in a fantasy world paid for by those living in the real one. There are simply times when violence is the only way to settle disputes.

It may seem ironic to a simple mind, but advanced weaponry is the best way for one to remain at peace. Being easier to abuse doesn't lead to less violence in a world where evil exists. War should be as horrific and unimaginable as possible if we really want to avoid it.

I love peace but I also understand that it sometimes comes at the expense of war.

Also, the Peace prize was one of five prizes. It wasn't the only thing he valued.

Some things conveniently or ignorantly left out here: People were using black powder and nitroglycerine (used for vasodilation now) explosives before dynamite. His invention reduced the chance of accidental detonation and made workers handling it a lot safer. His work on explosives was inspired by construction, not war.

Yes, his inventions were later sold for military use, and he indeed did not want to be known mainly for that. But that is in no way a negative point against his character. He did amazing work in his time that is worth celebrating.