There is a well-worn saying (and we should all try to wear it well) that the abuse of a good thing does not take away its proper use (abusus non tollit usum). So, for instance, the fact that Bobby Knight might use a chair as a weapon of his warfare does not destroy the additional fact that there is a proper use for that chair.
In his Rhetoric, Aristotle gives an elegant statement of this principle, because rhetoric is something very prone to abuse and therefore open to the charge of being inherently a Very Bad Thing. The use of speech and reason is distinctive to man, and so a man had better learn how to use them well.
Again, (4) it is absurd to hold that a man ought to be ashamed of being unable to defend himself with his limbs, but not of being unable to defend himself with speech and reason, when the use of rational speech is more distinctive of a human being than the use of his limbs. And if it be objected that one who uses such power of speech unjustly might do great harm, that is a charge which may be made in common against all good things except virtue, and above all against the things that are most useful, as strength, health, wealth, generalship. A man can confer the greatest of benefits by a right use of these, and inflict the greatest of injuries by using them wrongly. (Rhetoric 1.1 [1355a-b])