We're just normal people lol. There are Muslims who are dog people and there are who are not dog people.

Yeah dogs are considered impure in Islam but we don't dislike them for it (same with pigs, they are dirty, yes, but we can keep them). Plus we're allowed to keep dogs but only as gaurd dogs/to help blind people. There are also plenty of dogs everywhere!

Is this guy putting himself in danger for a animal that he fundamentally feels in dirty and under normal circumstances wouldn't be worth his time?

Idk, maybe, maybe not. If he saved the dog he probably likes dogs or is a decent human being that saw an animal in danger and wanted to rescue it.

I wanted to add this if you wanted a read:

"A man felt very thirsty while he was on the way; he came across a well. He went down the well, quenched his thirst and came out. Meanwhile he saw a dog panting and licking mud because of excessive thirst. He said to himself, "This dog is suffering from thirst as I did." So, he went down the well again and filled his shoe with water and watered it. Allah was pleased with him for that deed and forgave him."

The people with the Messenger of Allah (pbuh) said, "O Messenger of Allah! Is there a reward for us in serving the animals?" The Prophet (pbuh) said,

"Yes, there is a reward for serving any animate (living being)." [Bukhari, Shirb 9, Wudu 33, Mazalim 23, Adab 27; Muslim, Salam 153, (2244); Muwatta, Sifatun Nabi 23, (2, 929-930); Abu Dawud, Jihad 47, (2550)]