John Stuart Mill
"However unwillingly a person who has a strong opinion
may admit the possibility that his opinion may be false, he
ought to be moved by the consideration that, however true it
may be, if it is not fully, frequently, and fearlessly discussed,
it will be held as a dead dogma, not a living truth."
If it means anything to you, I'm a hardcore post-structuralist liberal.
But of course, these labels hardly mean anything without context.