Intellectually, I believe God does love us all, although my feelings might say otherwise at times. If I didn’t believe, almost everything else in Catholicism would be difficult for me to accept; faith in His love is crucial. Hypothetically, even if it were only one human being in existence who actually needed salvation, I believe Jesus would still offer himself up for that single person.
At times, I tend to think of myself as just one of His many children. However, I try to remind myself He cares for me as an individual, that He is aware of my every thought and action, and that He watches me with great love, sustaining my very existence. If He didn’t love or care for us, I assume He could just take us out of existence in less than a second. Or rather, He wouldn’t have created us in the first place, since He knew what we were capable of.
'Tis common for people to imagine God holding the same standards they do. It’s just like how people who tend to be hard on themselves imagine that others, including God, can’t possibly love them. There are also people who find it hard to forgive the weaknesses and faults of others and so find it hard to believe that God can. Some people have had uncaring parents or guardians, and they might project these experiences and feelings onto God.
When we think it would be hard for God to love or forgive, it’s usually because we find it hard to love or forgive, but God’s not us.
Let the wicked abandon his way and the evil one his thoughts. Let him turn back to Yahweh who will take pity on him, to our God, for he is rich in forgiveness; for my thoughts are not your thoughts and your ways are not my ways, declares Yahweh. For the heavens are as high above earth as my ways are above your ways, my thoughts above your thoughts.
Just curious, but why don’t you include mass murdering-type people in your question?