This question is usually asked by atheists, but the first problem is that they have no objective moral standard by which they might say God's judgment is right or wrong. They may not like it. They may not approve of it. But these objections and preferences are irrelevant as to whether or not God is right or wrong for damning people eternally. The only way they can rationally assert that something is morally right or wrong is to appeal to moral standards outside of themselves. If the appeal is to what society says, this is dangerous since societies change and morals can become right in one generation and wrong in another.
Second, God is not the one torturing. To torture someone means to be actively involved in the action of inflicting pain. But God does not do this. God sends people to hell and they are tortured there due to the consequences of their sin and their rejection of God.