I'm ony guessing here, but:

From the image you presented, I'd say that SMF's claim is going to be that they instructed TargitInteractive to only send this ad to addresses that had opted in.

Like you, I'm very careful about reading Ts and Cs, and I always use a webmail box (Yahoo etc) when responding to offers that I feel present a danger of generating spam.

Please let us know what the response is(if any).