Wouldn't it be sad if Sayid ends up shooting Nadia? That'd be three romances shot dead by his own hand. If so, our torturer's fatal flaw will seem to be that romance and sentiment are no longer possible for someone such as Sayid has become. Or, that perhaps Sayid's astute abilities, the ones which make him such a good torturer, are blinded whenever romance enters the picture. Ergo, Ben's implied suggestion that perhaps he should just be a killer, and not a lover. Three attempts at happiness, and all three ended in a brutal death of the source of that happiness. Best if he just avoids seeking happiness through love, and be satisfied with the gun.
Ben, too, seems to have embraced that philosophy in his own life. To be a manipulative SOB, you can't be having a giddy romance, or even wanting to.