Fitness tracker maker Fitbit (NYSE: FIT) was a Wall Street darling last year, soaring from its IPO price of $20 to over $50 between June and August. But the stock has since plunged over 70% due to ongoing concerns that the company’s high-growth days are over. I don’t like to kick a stock while it’s down, but I think the bears are right about this beaten-down stock for four simple reasons.