I wouldn't say completely implausible. Considering Oklahoma seems to be a target one way or another; that McVeigh could be influenced by Islamists without any apparent "connection" (other than what was hidden by the Rats at the time), it seems quite plausible to me that Islamic students would seek out and target the less, um, sociable to do their dirty work for them. Plus demand silence of any relationship. Brainwashing IS a specialty of terrorists, after all.
Is that too tin-foil?
What is it with the Feds in the OKC area anyway? There's more going on around there than meets the eye. It's enough to make a sane person put on the tinfoil hat.