When trying to understand what they mean, I generally find two causes:

For the latter part, there's not much I can do. The best way to deal with irritating and annoying people is to ignore them, in the hope they just go away. There are evangelists everywhere. GPL fanatics are mostly irrelevant and they don't bug me so I can ignore them, except maybe the ones working for FSF or the ones actually drafting the GPL but then it's their job to do so. Heck they don't complain about paid Microsoft evangelists. Amusingly (or sadly) most people whom I hear complaining about GPL fanatics are actually anti-GPL fanatics themselves.

Now for the viral part, well yes GPL is viral and I have no problem with that. The main complaint I hear is that by using GPL I prevent others from using my work and instead I should be using a more liberal license such as MIT or BSD.

This is false on two levels.

First by using GPL I don't prevent others from using my applications. At the contrary, they are free to use them as they wish and they have free access to it and any updates. I don't either prevent others from reusing the source -- as long as their application is also GPLed, meaning I will have access to it.

But then that's exactly what they mean -- they want to be able to access my source and embed it in whatever software they have. If the software is commercial and close sourced I'm sure to have a problem with that and that's exactly why I choose the GPL in the first place, i.e. that I don't want others to take whatever I wrote and monetize it without retribution. I would, however, be more than happy to dual-license it against a reasonable compensation.

In the case the target software uses a more liberal license, say, MIT-based one, using GPL still prevent it from being included. That may be but again dual-licensing is always an option, although I would not degrade the original license from GPL to MIT since it would undercut the protection granted by the original GPL version. In this case I would instead advocate including GPLed code with permission from the author. Amusingly most people will refuse that because they are anti-GPL fanatics.

Now note that I'm not myself a GPL fanatic. I use GPL when I think it suits me, mostly for home projects that I want to open but where I don't really expect others to embed them -- i.e. applications instead of libraries. My idea is that by publishing an application as GPL, nobody will be able to legally take it as-is and sell it, yet however if any feels like it they can use it and extend it and hopefully give me back patches (which has happened in the case of RIG.) They can make money by using the software if they wish, directly or indirectly, there's nothing wrong with that (it's their effort as a user, not mine, also true for RIG BTW.)

If I were to create a library and wanted others to use it, then yes I would consider a more liberal license such as MIT. Note that here there are two cases. If I just want to make it available to anyone for free, I'd just put as MIT and maybe ask for a credit line and/or keep an embedded comment line with credits -- in which case the compensation is hopefully fame and showcase. However if I wanted to make money from it I could dual source it as GPL and closed, the latter for a fee -- GPL apps could pick up the library (they wouldn't pay for it anyway) and make it popular and closed apps could always buy a license.

To finish I'd say that where ever I said GPL earlier I meant GPL v2. Version 2 seems just fine to me right now. GPL v2 is about giving rights back to authors & users whereas the new version 3 seems to follow some kind of political agenda designed to restrict the rights of a number of people.