Dr. Chee cites the possibility of nationalistic Chinese nationals causing trouble within Singapore. So are we to reject foreigners who express nationalistic sentiments? How are the authorities supposed to screen for nationalistic sentiments?
Dr. Chee also cites again the example of radicalised Bangladeshi foreign workers who were recently arrested in Singapore. Correct me if I am wrong but I believe most of these Bangladeshis were radicalised after they arrived in Singapore and not before. So how would pre-emptive screening have helped? And I suppose the authorities would already have a list of dangerous individuals who are denied entry into Singapore.
It also seems strange to me that while many have criticised Denise Phua's reference to foreign workers as "walking time-bombs", not many appear to object to Dr. Chee's reference to foreign workers as a potential security risk.
In the end, while Dr. Chee's argument might be appealing on the surface, it is simplistic and erroneous in my opinion. He may dispel counter-arguments as straw man arguments but it is because his position is unclear and lacking in details that straw men are easily constructed out of it.