Critics nonetheless mewl argue that patents "stifle innovation." This is like arguing that requiring people to pay money at a restaurant "stifles feeding," or that making it illegal to steal a UPS truck to start a delivery service "stifles entrepreneurship." (Doubtlessly, when Thomas Edison denied Nikola Tesla the $50,000 he had promised him in exchange for spending several sleep-deprived months improving Edison's DC generators, Edison likely felt that honoring the contract would have "stifled" his company's innovation.)
It is unlikely that making it illegal to steal a UPS track to start a delivery service "stifles entrepreneurship" but of course it is an empirical question. In the case of patents the evidence is in: patents stifle innovation. Only evidence can refute evidence - theoretical arguments, feelings, and analogies are irrelevant.