The danger I suppose of killing or deporting anyone who's just a suspect is that that becomes a recruiting message for others and might lead to more threats.

The other question is if they are born in the UK, where do you deport them to? If their family has lived in the country for generations?

And although violent terrorism is immediately shocking and causes great distress and death and injury, it's not the biggest killer. Should we not be considering treating the same those who knowingly cause excessive air pollution (cited as killing thousands a year, VW cheating on their emissions declarations), or aggressively flogging products that cause heart disease and cancer (fast food, alcohol) (ok in this case you could say people choose to use those things but they know how to advertise to essentially make sure people buy lots of them.