Like it or not, regional airlines are the "entry level" job for the majority of folks out there. Each pilot that applies to a regional has a particular reason why they are applying.
Almost always it's to build time to further their career (in some form or another). If you want to go to a regional and stay an FO or bail out for something else after a year or two, so be it. That's YOUR chosen career path. You're not "taking" a job from somebody else the way I see it. If that other person is more qualified for the job- he/she will get it over you.
If going to a regional to build turbine time is your goal before you move to a corporate/charter/fractional job- that's nothing new. I know plenty of folks that have left regionals without upgrading to PIC at those companies. I also know a handful of folks that worked as an FO at a regional in order to gain operational experience as a line pilot before seeking out a management job somewhere else in the aviation world.
Not to mention the number of people that try it out and then leave aviation entirely.
It's your career path and you make the choices. Don't worry about what others will think- the honest truth is that they don't have to know what your plans are (unless you feel inclined to tell them).
Simply put- we're all "career" guys. Some careers just progress differently and have different end goals than others. Don't allow the thoughts/opinions of others to sway your own goals and options.