Okay, so I see the current conversation, but before I enter that I would like to cover all the
previous questions, starting with the OP.
"What do you folks think of ideology?" I believe an ideology is a persons way of expressing their values through their "ideal world", which is expressed in various ways.
"Should everyone have one?" Point is moot due to..
"Does everyone have one without knowing it?" So long as that person is (or was) part of some civilization or community, yes.
"Should a person be ideologically consistent?" Depends on what you mean. If you mean that a person's ideology should match up with their values, that is inherent due to connect. However, if you mean their ideology itself should be consistent, then yes, to a fault, as exceptions to rules may seem inconsistent unless you apply them to the person's core values. And thirdly, if you mean their actions should be consistent with their ideology, the answer is yes, if they want to be taken seriously. Unfortunately, this is not always the case.
"Are some ideologies more correct than others?" Well, since an ideology is basically a person's "ideal world" i.m.o then technically none is truly more correct, as anything different than your ideology would be incorrect. However, some ideologies are in fact, much more effective in practice than others (like say democracy over anarchy). After all, if this were not true, then we would have many more popular ideologies than the ones were currently have.
"How does one discern a correct ideology from an incorrect ideology?"
Through research and experimentation. After all, it is best to look at the past to research an ideology, and the only way to truly know how it is in practice is to practice it (like numerous "utopian" societies that have died out) on a larger scale. Ultimately, the most effective/correct ideologies will find their way through to popularity and widespread implementation.
"How are conflicts between ideologies to be resolved?"
Like Putin said, with politics (debate) or violence (war). No matter what you do, one of those two will be used eventually to settle the dispute.
"Under what circumstance should one abandon an ideology?"
When it is shown/proven to be ineffective in practice or inconsistent with your values, actions or itself.
"Do you agree that there are no real challengers to liberalism?"
Well given your definition of liberalism, I would have to say yes, in a way. While numerous systems are falling to democracy and market economies (i.e communism), I would say the biggest challenger to liberalism is "corporatism". To define corporatism: "the organization of a society into industrial and professional corporations serving as organs of political representation and exercising control over persons and activities within their jurisdiction". After all the basis of democracy is "rule by the people", but by and by the U.S (at least) is moving toward rule by special interest groups, specifically corporations. If this were not the case there would not be so many corporate lobbyists near Congress.
Hopefully this does not x-post with too many people.