By Dan Weil Financial stocks haven’t fared well this year, with the KBW Bank stock Index dropping 15.5% year to date. Financial stocks haven’t fared well this year, with the KBW Bank stock Index dropping 15.5% year to date. That compares to a 14.3% fall for the S&P 500. But the weakness in financial stocks may provide some buying opportunities. “The macroeconomic backdrop for stocks in the financial sector has been challenging year-to-date,” Wells Fargo analysts, led by Mike Mayo, wrote in a commentary. That backdrop is “driven by significant volatility in equity markets and interest rates, [d…