Every major news station has political bias. Liberals only get "offended" because Fox News has as much conservative bias as the stations like CNN and MSNBC have liberal bias. It's not a good thing or a bad thing, it is just the way it always has been and always will be.
There is really no doubt that FOX News has a political agenda backing a conservative platform. On the whole it is only problematic in that they refuse to drop the idea that they are providing fair and balanced news coverage. If anything isn't the fault of a leading Democrat, they just didn't have time to research enough things to connect the 47 dots back to said Democrat.
Frankly speaking I think all of the networks are politically biased, some of them more, some less. Fox News has always targeted Obama and other democrats through their shows. This channel was created to be a counterweight to the left of center bias which dominated the airways prior to their creation. It in short is intentionally biased right of center.
It is normal for a private channel to be biased, as its owners might favor certain opinions. In the past, Fox News have been accused for one-side analysis and for promoting certain attitudes towards tragic incidents. In my opinion, Fox News are biased, since they do not consistently provide independent, reliable and valid information to the public.
I think it is just human nature to exude some sort of bias, especially when reporting on touchy issues. However, I do not think that Fox News goes out of its way to be biased nor do I think it has any kind of hidden agenda. I have heard comments here and there, whether it was a competing news network or a blog of some sort, that both Fox and CNN are biased. I personally don't agree with these critiques. Overall, I find they both present pretty much fact-based reporting and both have on-air personalities that, at times, reveal perhaps their political bent but again, I think that is human nature.