Many renowned philosophers have proposed many different systems for ethics and politics. Some are more liberal than others, but making an exhaustive list is quite the task.
It's just a single exemple, but Jeremy Bentham proposed a system known as utilitarianism that in a nutshell boils down to "if someone wants to do something that makes them happy, and does not harm you, let them be".
Following this logic he arrived at conclusions about what should be allowed that are widely accepted now but were pretty revolutionary for the time, like gender equality and the decriminalization of homosexuality.