Rush Limbaugh is not strident, but he is direct. He is not above name-calling either, but he is most interested in making a point.
He is a radio personality, not so much shocking as compelling. His blunt honesty has resonance across the country. Most people in a center-right country love to trash government, even if they secretly get handouts here and there.
Like most radio commentators, getting ratings is what the whole role is all about. Yet unlike print or Internet, strident conservatives have remained a mainstay for decades, whereas the liberal attempt, Air America, did not last one year.
Strident conservatism seems strident, therefore, because there is so little liberal opposition to counter it. In that case, the fault lies with the content of the left, not with the right.
Columnists like Ann Coulter and Michelle Malkin are also strident people, but their rhetoric is a matter of personal style, not endemic to their political point of view. Whatever will attract more readers, that's what these ladies will put out.
Therefore, Conservatism in itself does not cause its adherents to be strident. Rather, the personality of the speaker or the rhetoric that sells the most, that determines the line and tag of strident conservatives, from Joe Pyne to Rush Limbaugh.