[crispyporkbites]

How many terrorists have entered US territory through an airport with a beheading video on their phone and then carried out an attack on US soil?

Answer: approximately zero

How many terrorists would be deterred by this policy?

Answer: none

How many ordinary people would be more likely to carry out attacks or harbour resentment towards the USA because of policies like these?

Answer: more than 0

[wang_li]

> How many ordinary people would be more likely to carry out attacks or harbour resentment towards the USA because of policies like these?

Someone who hoards beheading videos is not ordinary and it's perfectly in line with the international norms to be able to exclude undesirable people from entering into a country. E.g. Canada won't let people who have past criminal convictions enter, like a DUI.