Feminists need to stop comparing Martha Stewart to other women her age and start celebrating. — By now, you’ve likely seen the now-controversial Martha Stewart Sports Illustrated cover shot. At 81, she’s photographed with enviable cleavage, tousled fresh-from-a-romp hair, and a sweet, seductive smile. In a swimsuit, of course. She looks, in a word, amazing. Know what’s not amazing? The blow-back she’s received from women, under…