I think Rand was thinking more about his own mental state and the temptations of the Choedan Kal rather than the greater good that could be accomplished with it (I doubt he could have achieved the Cleansing with Callandor, for example).

There is still the overall risk that they represent, though - with Circles, you at least need to convince other rational beings to Link with you to accomplish things. The concentrated power of the Choedan Kal, though, puts too much power into a single entity's hand, so I understand his decision even if I think this was one of his weakest moments.