If you asked random people on the street to list the top ten words they associate with "ice," "hate" would probably not make the list. Maybe the top 50. Maybe. Just behind "Emperor Penguins." The poem shifts from the literal to the symbolic.
I think I know enough of hate To say that for destruction ice (6-7)
This statement is tantalizing. What does the speaker know about hate? We think that these lines are an admission that almost all people have known hate at some point in their lives. He's an honest speaker.
Is also great And would suffice. (lines 8-9)
By the end of the poem, we realize that the detachment that the speaker has displayed all along is an example of just the kind of cool reason that can be so destructive when coupled with hate. Scary.