Universalism enjoys a certain general emotional appeal. But its emotional appeal depends on the examples used to illustrate universalism. If it's the fate of your loved ones, then it's very attractive.
Suppose Anne Frank wound up in the laboratory of Josef Mengele. Suppose she was subjected to the infamous Nazi "medical" experimentation. You can Google the subject.
If universalism is true, let's say both Josef and Anne go to temporary hell when they die. In universalism, hell is really Purgatory.
If, after however much remedial punishment, Josef says uncle before Anne, he beats her to heaven.
Anne will not be allowed into heaven until she forgives Josef. Anne will not be allowed into heaven until she loves Josef. Anne will continue to be punished until she is bullied or terrorized into submission.
Seems to me that whatever abstract or general appeal universalism may have, it lacks universal appeal. Once you begin to cite hard cases, which can be vastly multiplied, it instantly loses its facile emotional appeal.
At this point a universalist might counter that according to the Gospel, God can forgive very evil people. And we should forgive whoever God has forgiven.
But while that's true, that's shifting ground from the the emotional appeal of universalism. To a great extent, that's the opposite. It's emotionally repellent to the victims. It cuts against the grain of human nature to overcome that moral and emotional aversion.
As such, a universalist can't consistently deploy both lines of appeal. He can't begin with an appeal to moral intuition, then when that backfires, switch to a counterintuitive appeal to the Gospel. Those are two opposing principles.