Jesus of Nazareth said, "love your enemy" (Luke 6: 27-38)

he didn't say, "kill your enemy"

so why do Bush and Blair call themselves Christians?

because they are are part of a proselytising fundamentalism which stretches back to when Christianity became the state religion of the Roman Empire - when Bush talked about a "crusade" in the context of sending his army to invade Moslem countries, that's exactly what he meant