They are screaming on the streets because the social services that might assist them have been increasingly gutted by every president since Reagan. What you seem to be hinting at is doing away with undesirables who are a drain on your eutopian society. Put them someplace where we can "manage" them.
And homeless does not equal crazy and screaming.
Crazy doesn't even equal screaming. Most crazy people are quite grateful for small kindnesses. I went out in the rain once to give a crazy homeless person a dish of hot beans and rice. She came by the next day to give me back the dish and spoon, washed. I saw a vendor give her an orange.