We know that Liberty is not only the only justifiable state of things, but also a very practical state (the far most practical for those who don't have politicians as friends and business-partners). No State can be justified without violence (which again can't be justified if we admit the self-ownership of individuals). No coercion and aggressive attacks against individuals and their non-aggressive communities can be justified. No tax is justifiable. No forceful legislation can be justified. No non-aggressive actions of individuals can be outlawed.
But justifying is sometimes not enough. Sometimes you also need examples, especially when trying to convince the masses of the ideal of Liberty. Thankfully, examples are in plenty. Empirical data, flawed that it is, is overwhelming when it comes to show how Liberty is superior to the State and its applications. Free economies blossom while socialist economies fade into stagnation and decay. Taxes decrease wealth and prevent individuals from earning their way up in standard of living and well-being. Regulations hurt companies and growth and create unemployment and result in relatively lower incomes (average income can be high or on the rise in a socialist economy, but only compared to its own previous norms).
However, when it all comes down to it it's not about the number of examples and empirical proof. It's about Liberty and it's friend, Justice. It's about supporting a free society of free individuals and fighting for its creation (re-creation in relative terms). Because what if Liberty would create poverty and aggression? What if Liberty would have the same effects socialism has on society? Of course it could never, but a thought-experiment is perhaps worth the while. Would we sacrifice Justice and Liberty if they created poverty and aggression? We haven't when it comes to socialism, but would we in the case of Liberty?
In the end all the statistics and data doesn't matter when choosing right from wrong. Thankfully, Liberty and Justice have all the evidence on their side (besides the logic of course), but that is the wrong focus to put on things (although a very practical when arguing with the Left).