Ideological labels are the bi-product of having a two-party system, more so now than in the past when both parties had "bigger tents" and there was more consensus-building rather than confrontation between and within the parties.
The "label" attached to the issues you cited as examples - the war in Iraq, social security, abortion, health care - are the result of the position of the two parties (yes, both parties have official positions and platforms -
Repub and
Dem
Only the very hard core ideologues on both ends likely support all of the positions of their respective party.
At the same, more Americans are moving away from party labels or conservative/liberal labels and are identifying themselves as Independent or moderate, because, as you noted their position varies by issue. I assume they base their votes by prioritizing the issues, along with the character, intelligence and other personal traits of the candidate.
As long as we have a two-party system, which I personally believe is much better than any multi-party system, the ideological labeling is a necessary evil.