But lets take your claim as given, namely that some classes of people are so dangerous if we don't pay them they'll harm us. If I thought you were right, then I'd probably turn to the Brexiters and Trumpkins for a solution. Are you really claiming that the poor are basically just gangsters and terrorists?
I'd estimate at least 90% of people living under the poverty line would never choose to commit a violent crime or property crime if their survival needs were assured. Malum prohibitum crimes and regulatory infractions are another story. Having more money means you can smoke higher-quality marijuana, and usually with less police interference. Having more money means you can pay speeding and parking fines without spending any nights in the county jail.
"Poor people" are not just one big homogenous group. They have their righteous saints and their sleazy lowlifes, and everything in between, just like every other economic class. The former deserve society's help, whereas the latter can sometimes be bribed to behave better.
Welfare doesn't stop the terrorism that still happens in places that have welfare, because those terrorists aren't murderously mad about being poor. It certainly stops food riots, at least until the system collapses. The crime in the Chavez-unraveled Venezuela is quite different from terrorist activity in Europe.
Also, what's the point of making a quantifiable estimation (your "90%") if you have no actual data behind it? Just say you believe something based on observation; throwing out a nice round percentage to describe your belief, even as a figure of speech, does a disservice to real attempts to quantify phenomenon in a discussion.
Are my perceptions wrong? Do you have any evidence to support your claim?
Also, why can't vigorous policing - rather than paying tribute to violent criminals - also solve the problem?
If you pay someone $7.25/h to do nothing, that might be considered an incentive payment to not do work that does net harm to society.
While it would always be better to pay the $7.25 for something that might benefit the economy less in absolute terms, there is no "zero" that can be used to calculate a "net" cost of social welfare. Playing video games is not plowing a large vehicle through a crowd of people, or mixing fertilizer with #2 fuel, or strapping tiny backpacks filled with thermite and moisture-sensitive primers to bats, or cooking meth, or cooking krokodil desomorphine, or turning tricks in the park bathroom, or pooping in the neighborhood swimming pool.
One person can be very destructive, or at least thousands of dollars worth of annoying, before anyone would bother stepping in to check them.