Limits to the homo economicus version of rationality are also limits to the explanatory power of some aspects of introductory-level economics. They do not, however, compromise the case for laissez-faire. If anything, they strengthen it.
Public Choice Theory provides a window into the incentives of government, providing insight into how and why bad and unpopular policies stay in place.
Homo economicus got its start way back when two humans decided to trade. The rest was history.