Ayn Rand saw the obvious danger in that, so her criticism of Kant's ethical theory is understandable, even if she did make a straw man.

We should take a given action because it is the rational thing to do, not because it will benefit us or someone else.

Okay but there is still a fallacy, as was elaborated on by Peter in #2.

Kant said to do things because they are right, not because there is any benefit from doing them. There is one top morality I can think of where something like that could be applied to the real world: altruism.

Perhaps the first philosopher to suggest a teleological reading was John Stuart Mill. In the first chapter of his Utilitarianism, Mill implies that the Universal Law formulation of the Categorical Imperative could only sensibly be interpreted as a test of the consequences of universal adoption of a maxim. Several 20th century theorists have followed Mill's suggestion, most notably, R. M. Hare. Hare argued that moral judgments such as “Stealing is wrong” are in fact universal prescriptions (“No stealing anywhere by anyone!”) And because they are universal, Hare argued, they forbid making exceptions. That in turn requires moral judgments to give each person's wellbeing, including our own, equal weight. And when we give each person's wellbeing equal weight, we are acting to produce the best overall outcome. Thus, in his view, the CI is “simply utilitarianism put into other words” (Hare, 1993, p. 103). More recently, David Cummiskey (Cummiskey, 1996) has argued that Kant's view that moral principles are justified because they are universalizable is compatible with those principle themselves being consequentialist. Indeed, Cummiskey argues that they must be: respect for the value of Humanity entails treating the interests of each as counting for one and one only, and hence for always acting to produce the best overall outcome.

There are also teleological readings of Kant's ethics that are non-consequentialist. Barbara Herman has urged philosophers to “leave deontology behind” as an understanding of Kant's moral theory on the grounds that the conception of practical reason grounding the Categorical Imperative is itself a conception of value. Herman's idea is that Kant never meant to say that no value grounds moral principles. That, she argues, would imply that there would be no reason to conform to them. Instead, Kant thought the principles of rationality taken together constitute rational agency, and rational agency so constituted itself functions as a value that justifies moral action. (1993, 231) Herman's proposal thus has Kant's view grounding the rightness of actions in rational agency, and then in turn offering rational agency itself up as a value. Both Paul Guyer and Allen Wood have offered proposals that differ from Herman's in content, but agree on the general form of teleology that she defends as a reading of Kant. Guyer argues that autonomy itself is the value grounding moral requirements. Moral thinking consists in recognizing the priceless value of a rational agent's autonomous will, something in light of whose value it is necessary for any rational agent to modify his behavior (1998, 22-35). And Wood argues that humanity itself is the grounding value for Kant. While the second Critique claims that good things owe their value to being the objects of the choices of rational agents, they could not, in his view, acquire any value at all if the source of that value, rational agency, itself had no value. (1999, 130; see also pp. 157-8)