This does not, in this case, mean that one should not deceive those that they argue with. It means that one should not lie to themselves about what their underlying position on an issue in contention is.
When engage in an argument over any issue of substance one should always strive to be cognizant of what one’s aims truly are, irrespective of what tools of debate one uses upon others. This is especially true when one has a measurable chance of winning the argument and enacting or preventing change to a subject or system.
The above is not just mere philosophy or some exercise in moral rectitude; it is a matter of pragmatic necessity. If one is not honest with one’s self about what is desired, it is possible, probable even in a more complex, real world scenario, to completely win the argument and not come close to achieving the goals one actually desires.