Where can we draw the line and still maintain our humanity?

Look at the strain on public resources - taxpayer money:  unemployment; homeless shelters; mental health, counseling, and vocational services; medical services.  Costs on the criminal side:  police ; EMT paramedic ; sheriff; jail and food; public defender; prosecutor; judge; courtroom resources spread thin; probation; prison; parole.  One person could cost the taxpayers a ton of money over the course of their life.  

Historically, life has always been a battle for resources  - those who thrive will procreate and live on.  Not so anymore.  We've fought our animalistic past by striving to create a system that supports everyone, and those who are in the top 20% of earners (whether they were born into it or worked harder than the other 80% of the population) are paying over 85% of the total federal income tax collected.  At what point does the burden on one's back, break it?  I think we're seeing it now.