I suppose it depends how you define purpose - I mean if you know something is going to have some effect, is it part of your purpose or not?

If it's something you would rather not happen, probabaly not. If it's something you would like to happen, yes, even if it's only a secondary purpose.

So in this case I'd think that helping make the war more likely probably would have been one of the purposes of those who made the tape and made sure it got to Al Jazeira TV (who might not necessarily be the same people.) But I would think that for the TV Station such a consequence would be an unwanted secondary effect.

On the other hand, for at least most proponents of the war, the inevitable civilian deaths are surely an unwanted effect. The only people who might actually want such deaths - apart from the psycopaths you get from time to time - might be people who would see them as a valuable way of generating hatred towards America.