It is one of the many paradoxes of modern liberalism that it tolerates the existence of ideologies that are profoundly illiberal. In any given liberal society, we can expect to come across all manner of ideologies—extreme right, extreme left, and religious fundamentalists—whose values stand in complete antithesis to modern liberalism.
If any of these ideologies were ever to achieve dominance, then it is likely that liberalism as we know it would cease to exist and that a completely different political paradigm would take its place.
This raises the question as to how modern liberal societies should deal with these ideologies. One possible approach is to say that such ideologies should be tolerated, but not respected. That is to say, those who hold such ideas have the right to believe them and to disseminate them, but not the right to have them treated with respect.
Toleration, as opposed to respect, of illiberal ideologies is invariably practiced within a specific legal framework. One can only tolerate that which is legally permitted. Beyond that, one cannot reasonably go.
In a liberal society, laws can be passed that place restrictions on the promotion of illiberal ideologies if they incite violence or other criminal actions. In this way, liberal societies can uphold important values such as freedom of speech and freedom of religion while at the same time protecting society from harm.
Indeed, the harm principle is very important here. The general approach to illiberal ideologies in modern liberal societies is to tolerate them just so long as they don't cause harm. This could mean psychological harm as in the case of hate speech or physical harm in the form of violence.