Voting is probably irrational unless you enjoy it. My vote won't matter unless the election would otherwise be a tie which probably implies that one candidate isn't much, much worse than another. But your drug conclusion doesn't follow from marginal analysis because my giving, say, $1000 to the Mexican Mafia might increased the murder rate by enough to make my actions immoral.

By the Kant quote I shouldn't not grow food because if no one grew food billions would die. The Kant quote violates Consequentialism although since Kant is a famous philosopher and my objection is obvious I suspect he would have a good counter-reply.