None of those are examples of refugees. Ahmad Rahami entered the U.S. about 21 years ago, in 1995, and was the son of an asylum seeker; the Tsarnaevs were also asylum-seekers (2002) and were full-on American citizens when they committed their crimes, so it would seem that they were radicalized in the U.S. The San Bernardino shooter Syed Rizwan Farook grew up in Riverside, California and it appears his wife Tashfeen Malik immigrated on a marriage visa, just as I am trying to do with my own wife right now. Do you want to keep my wife and I out of the U.S., too?
Asylum seekers are not the same as refugees. Asylum seekers have some reason to believe they will be unjustly targeted when they return to their home country, implying there is something special about them compared to other citizens of the same country. Syrian refugees, in contrast, are in danger simply by existing in Syria at all. They are not targeted for their beliefs or anything they have done; it’s simply dangerous to be in Syria right now. All else being equal, I would expect refugees to have a lower probability of being radical than asylum seekers.