I can't find evidence for the moment, but this is what it suggests to me: that the interview was "screwed" out of him, in a sense, along the lines of the expression "apretarle los tornillos". I'll try to find confirmation.

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Note added at 7 hrs (2015-05-13 07:40:04 GMT)
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In the context I think "reluctantly" is the right translation. I added "under pressure" to clarify how "a tornillo" might come to mean this.

Maybe it's lunfardo, but I don't think so. I can't find it in any lunfardo glossary or dictionary (of which there are several around). Tornillo o torniyo can mean intense cold, but I don't think that's relevant.

I think it's got more to do with the expression "metido a tornillo", implying something that's been forced in somewhere it doesn't really belong. And that usage is not confined to Argentine Spanish:

"Pues sí, para hacer un buen edificio se deben hacer unos buenos cimientos, no tenerlos añejos, podridos y heredados del anterior "propietario" de la casa, que nos los metió a tornillo sin posibilidad de elección."
http://www.foro-ciudad.com/lleida/cambrils/mensaje-12083633....

This refers to Franco imposing the current monarchy on Spain.