I think it's a bit short-sighted to label any renewed scrutiny of the acceptance of Syrian refugees as ridiculous hysteria. There is good evidence, though it it still evolving, that ISIS has leveraged the Syrian refugee situation to help facilitate the attacks in Paris. Whether the attacker truly entered the EU posing as a "refugee", or was using a mis-appropriated passport remains to be seen. But, it is wishful thinking that the passport, only reportedly found on one attacker was part of some "false flag" operation on the part of ISIS and a real objective of the attacks was to get Westerners to turn against Syrian refugees (whom I doubt only consist of Muslims).
While I think that it's wrong to categorically now refuse Syrian refugees, I don't see it as "hysteria" to call for a pause in the operation to re-examine the process to see if there's any lessons to be learned (either from any news out of Paris, or any other loop-holes that can be identified and closed) before such programs are resumed. Lost in all of the media hand-wringing I hear today is that many (most?) of the state Governors, but perhaps not all, are not calling for a permanent halt to assisting in the resettlement of Syrian refugees within their borders, but only a "stand down" to reassess the security of the processes. Take our Governor, for example, here's what he said (bolding mine): "Michigan is a welcoming state and we are proud of our rich history of immigration. But our first priority is protecting the safety of our residents. Given the terrible situation in Paris, I've directed that we put on hold our efforts to accept new refugees until the U.S. Department of Homeland Security completes a full review of security clearances and procedures." He also later assured people that the state will resume the resettlement program, and that he also is still planning on increasing the number of refugees that the state can assist. Note that he isn't making additional demands or requiring 100% assurances. I'm curious what part of this approach that people find unreasonable?
We are basically taking the same approach that we did in grounding all US air traffic for several days after 9/11, in a similar "pause", even though only ~0.00005% of the air passengers on that fateful day were hellbent on mass murder.