That kind of thinking wld make him evil and as lowly as danzo and as u know evil never prospers.
Evil never prospers in fiction, no, but it does in real life.
Anyway, I'm not sure if you would call him really evil. He doesn't do it, because he's a mindless murderer, he just considers it adequate revenge for the massacre of his clan. There's a slight difference between killing because you can and killing because you want revenge. Sasuke falls into that second category. He's focused on his revenge. I don't think he enjoys the thought of killing, but killing those people would serve his need for revenge.
At the moment he doesn't care about anything else than his revenge and if killing let's him fulfill that desire, he will do it. He'll be considered evil for that and a cold hearted murderer, but then people would have to ask themselves if the rest of Konoha aren't murderers too. They are shinobi and therefore are eventually required to take missions where they have to kill other shinobis. Their village would still consider them as good people because they did it to protect the village, but the family of those people whom they killed, will consider them as cold hearted murderers.
Murder is still murder, no matter the reason. Be it protecting your village or seeking revenge, in the end it comes down to the fact that they killed people.
The only reason why Sasuke gets grief for his desire to kill the whole village, is because we don't condone the murder of innocent people. Yet, that is what happened when they killed the Uchiha clan. Yes, the culprits were of that clan, but most of them wanted to live in peace, yet they didn't get that chance.
So, even though Sasuke has a ****ed up view of justice, in a way he does what shinobi do all the time, only he follows no orders of a village.
Hm, not sure if my point came across. Sorry if I confused you ^^;
Anyway, I don't say he's allowed to kill the entire village, I just understand why he would do that.