Consider the qualifiers in Blair's statement: "...what I wouldn't accept is that [Hussein] was not a threat and a threat in WMD terms..."
The primary loophole is the word, "was." When exactly? In 1988? Who's disputing that? The secondary loophole is the word, "threat." What is the degree of this "threat," and who exactly is at risk? More to the point, is this a threat that warrants pre-emptive invasion by Western forces? The tertiary loophole is the phrase, "in WMD terms." Does this mean that Hussein still had a couple of artillery shells with 16-year-old chemical warheads (of questionable viability)? Or does this mean that he had amassed "stockpiles" of chemical and biological weapons, had deployed them for immediate use, and was continuing aggressive programs to acquire more (including nuclear)?
Yes, Hussein was a "threat" in WMD terms. But that's quite different than asserting that the United States was in such imminent danger from Hussein's WMD that we needed to "defend" ourselves with a pre-emptive invasion in 2003. Did we order 868 American soldiers to their deaths over a few old shells? Did this pose such a threat that 5,400 American soldiers should be wounded in combat? Is this our justification for maintaining over 130,000 troops in hostile territory? If so, then what of North Korea? What of Iran? If the world is such a dangerous place, then what have we gained by stretching our military so thinly? Are we really that much safer, and are our troops really that expendable?