It's consistent because the Libertarian platform defines what they consider natural rights to be, and government protection which upholds those is perfectly fine while other government interference is discouraged.

Any other platform also does the same (i.e., Dems think of universal healthcare and a minimum income as natural rights) and push for government protection of those standards, but they also use the government as a balancing force to correct what they perceive as intrinsic unfairness in the system. Usually these sorts of actions end up doing more harm than good, and libertarians usually oppose them.