Here's at least one reason why Jensen's motion on selective prosecution isn't the moral equivalent of the guy who complains that other speeders did not get tickets.
Using state facilities for campaign work is not intrinsically wrong. It is wrong because it is prohibited. It is prohibited, at least partially, because we don't want to give incumbents an advantage in the political process which is, after all, a competition. Its sort of like the rule against traveling in basketball. It sets the rules of the game.
To enforce those rules against one side but not the other, defeats the very purpose of having the rule in a way that ticketing only some speeders does not. It isn't just that its unfair to Jensen. It tilts the playing field in favor of the side against whom the rules have not been enforced. It doesn't just hurt the poor schmuck who got caught, it undermines the fairness of the entire system and undercuts the purpose of the rule which was to level the playing field.