This is spurious logic, because the Libertarians don't have a chance of actually winning.
Elections aren't decided by chance. If a Libertarian candidate appears on every ballot as his opponents then he has the same "chance" to win. If Libertarian candidates only appeared on half or one-third of the ballots then I'd agree with you. In that case they'd have no chance of winning.
We're you aware that Libertarians have held state assembly seats since 1979? Granted, no Congressional seats yet but it's only a matter of time. Eventually enough people will grow weary of Republicans and Democrats and you'll begin to see more Libertarians getting elected in higher office.