An ideologue is someone who doesn't let the facts get in the way of their beliefs and principles. I have come to believe that most people are actually ideologues, in that they are quite rigid in their political and social views. Therefore they find it hard to change their basic set of principles in response to the facts of experience and history. There are strong ideologues, who think and talk about politics alot, and weak ideologues who don't give politics much time or thought at all. It can be very difficult for a person to break out of their particular ideological cage. Indeed, most people find it a particularly comfortable place to live.
Like most people, I have been quite ideological in my past. That was particularly the case during the 80s, after I had become a neo-conservative. I was, well, almost arrogantly fanatical at times in my views.
Ideologues generally don't discuss honestly with others of differing views but instead talk past each other, mostly uninterested in the other's views. Instead of listening openly and receptively to the arguments and facts that others present, they are generally seeking strategies to defeat the other's point of view. It's the conquest of one's worldview over another's that provides the frisson.
It seems to me that ideology has become more prevalent in America during the last few decades, as most things political have become more polarized. This has been exacerbated by the advent and growth of cable television, talk radio, and networks that have a strong ideological point of view (e.g. Fox News). In previous times, the media had a political view, but they kept it more hidden and tried to give the appearance of complete neutrality. Perhaps CNN is the most like this these days.
The larger American political parties during the 20th Century used to be fairly non-ideological, primarily because they were coalitions of groups who didn't always agree in every principle but still had to get along in order to gain and hold power. The Democratic Party from the time of FDR was a coalition consisting primarily of Southern conservatives and northern liberals. The Republicans tended to be a coalition of northern moderates and conservatives and big business, free-market advocates, as well as some minorities who still admired Abraham Lincoln.
These days, the Democrats remain to some extent a diverse coalition of pro-business and hawkish neo-liberals, traditional liberals, environmentalist and peace activists, labor unions, and minorities, with no consistent ideological position. However, the Republicans have, since Ronald Reagan, become a much more homogenized, ideologized party. Moderates, let alone liberals, are not particularly welcome these days, and a strong conservative (or neo-conservative) orthodoxy is enforced.
The longer I live, the less ideological I have become. I have come to realize that no one ideological worldview has the entire truth, and that we need to constantly be listening to those who differ from us in order to see if they are seeing something we don't. This is a pragmatic approach to some extent, in the sense that it refuses to see things in absolutist terms but prefers to remain open to what experience brings.