412/659 MPs voted for the invasion, on all sides (LD and SNP excluded). It was the right thing to do based on the info we had, and even know we know that the WMD 45min claim was baloney it was still the right thing to do to remove Saddam from power. Ultimately it was the lack of planning to leave a stable government that made the whole war a mess, not the belief of doing the right thing.
Even if Stu has only voted Labour, it doesn't mean he was for the war. You can happily believe either way that the war was right or wrong, and still have an opinion on the continued use of Trident.