No. But, then, the terrorists have not been Afghanis. al-Qaeda recruited a lot of Saudis and Egyptians and others to fight in Afghanistan.
On the other hand, the whole notion of the quoted columnists is silly. Most of the terrorists involved in al-Qaeda have been upper middle class, even wealthy, recruits, but Israel is not handing out welfare checks to the Palestinians, so it appears that welfare only encourages terrorism against the U.S., not all terrorism.
The columnists quoted have taken one aspect of the sources of rebellion and terrorism (the poverty of the lands in which terrorism is involved) and pointed to a couple of disparate events to claim that welfare is creating terrorism (and crime).
There may or may not be some connections between some variations of welfare and some types or occurences of crime. In the articles quoted, however, we merely see facile right-wing misapplied logic (based on no serious information) that we are invited to wrangle over.
Based on the experience in the U.S. (and following the “logic” proposed thus far), I would have to conclude that the primary sources of terrorism, here, are based on an association with failures in the U.S. military and college drop-outs (Tim McVeigh, Ted Kaczynski, Bill Gates) so we should simply lock up anyone who enters the military or college, then fails or drops out.