Universal Salvation

While I really don't care if everyone goes to heaven or not, I can see why people hope everyone does, even notoriously evil ones. You can see and hear this when you pray the Fatima prayer.

O my Jesus, forgive us our sins, save us from the fire of hell, take all souls to heaven, and help especially those most in need of Your mercy.

What do the critics of universal salvation think when they pray this prayer? 

For some people, universal salvation is relying too much on God's love and mercy.  What about God's justice?

Once again, here I am trying to second guess God.  No one knows the mind of God.  Romans 11: 33-34

Oh, the depth of the riches of the wisdom and[i] knowledge of God!
    How unsearchable his judgments,
    and his paths beyond tracing out!
34 “Who has known the mind of the Lord?