Toleration as a political norm is demonstrably invalid because it is obviously self-defeating: must we tolerate the intolerant who attack peaceful dissenters? if muslims threaten and kill those who dare criticize their religion, and some people say won't tolerate it, are you to tolerate the former or the latter? Effectively, you cannot tolerate the deeds of one party without approving intolerance towards the other party.
That said, there is indeed a political system that promotes toleration
as a general phenomenon, and this system is Capitalism, not Socialism.
And obviously so, because Capitalism is a system where everyone
can create a domain where he can live according to his ideas unimpeded
by others, namely his property, whereas Socialism
(and after it the lesser forms of Statism) assumes
communal domains where everyone is the victim
of whoever manages to temporarily or permanently seize political power.