And we don't do that anymore. We did in the Middle Ages until the 1800s, afaik(haven't really heard of mainstream Christian denominations killing heathens in the 20th century unless we want to get into fringe groups of Christians), but that was so that we could keep Europe Christian at the time instead of letting it fall to Islam and Paganism. It's like how America executed it's own citizens accused of being Soviet spies during the Red Scare of the '50s.