First, let me state that Ron Paul Republicans are Republicans. We're not "liberals" that are trying to take over the GOP. Although many of us do have libertarian leanings, we are not Libertarians. We are Republicans.So why are we upset? In 2004, we dove into political campaigning, most of us never having campaigned before in our lives. We didn't do very well, but our support did continue to grow throughout the election cycle, even after we lost.
After the election of 2004, we reorganized and started training our people. We learned how to canvass, how the delegate selection process worked, and even scored some major victories in 2006 (like getting Rand Paul into the Senate).
Then 2008 comes along. We were ready for it this time. We obeyed the rules, did everything we were supposed to do, and even proved to be better at it than the other campaigns.
Unfortunately, this angered the GOP leadership - the ones making the rules and judging whether or not those rules have been followed. They changed the rules in 2004, hoping to give Romney a chance. The Evangelical stronghold of the Southeast (traditionally anti-Mormon) was changed to proportional victories, instead of winner takes all. (http://dougwead.wordpress.com/2012/08/31/romneys-revenge/). In 2004, the Southeast overwhelmingly supported Huckabee, allowing McCain to steal away victory from Romney.
So we adapted. We played by all the rules that we knew were created to simply put Romney into victory. And we continued to do well and win many of the contests. We knew we probably wouldn't take first place, but at least we were going to Tampa with enough victories to nominate Ron Paul and get to hear him speak. Also, we'd have enough delegates to influence the platform and the future direction of the party. And we were more than happy with that! In fact, that was one of our main goals all along.
In the days/weeks/months leading up to the convention, our victories were systematically taken away by the "rules committees" ... they wanted to keep us from having a plurality of delegates in 5 states so that they could silence Ron Paul and his followers at the convention. And they succeeded. Our victories were taken away through rule changes, ignoring the rules, and downright cheating.
And to make matters worse, passed new rules (without taking an actual vote) that will allow them to break apart any future grassroots movements. They took the power to decide the nominee away from the People and granted that authority to the party leadership.
That is why we are mad. We weren't given a fair shake. We played by the rules and were cheated against. If we had lost fair and square, then we wouldn't be upset. Sad, yes, but not upset.