I can't speak for Colgan, but at my last operator (another all-turboprop regional with low pay), it was definitely discouraged. While I was there, they enacted a policy that three sick calls within a specific timeframe was grounds for termination. The director of safety actually compared taking a sick day to stealing from the company! If Colgan's culture is at all similar to that (and I'd bet good money that it is), I understand her reluctance to call in sick.
I still think fatigue played a huge part in this crash--more so than will probably be in the final report. Had the FO been more alert (tough, after commuting in on a red-eye that morning), she might well have caught the slow airspeed before it was too late. Had the captain not built up a sleep debt from repeated stand-up overnights, maybe he'd have caught it, too.
Yeah, they screwed up the end game; that much is obvious. But there were
many links in this accident chain we can all learn from. Simply calling it "pilot error" and moving on is a cop-out.