Isn't that succinctly elegant?
The main issue is that carbon dioxide is a heat-trapping gas and we're putting more and more of it into the atmosphere. Even if the temperature trend line were stubbornly flat, carbon dioxide is still a heat trapping gas, and we're still putting more and more into the atmosphere.
Now, as to whether environmentalists are guilty in pointing to freakish weather as evidence of warming, think about it this way. If you know that the wiring in your apartment building is faulty and no fire has broken out yet, but a building a few blocks away happens to be on fire, are you wrong to point out to your neighbors, "That's what I've been warning you about."
Is that really the same as a guy who says he doesn't believe in faulty wiring making a joke about his too-cold refrigerator? A joke that never stops seeming hilarious to him?
1. heat trapping gas
2. more of it
That's it, people. That's really it.