From Michie (1982):

Competent medical and biological research authorities in various parts of the world are concerned about genetic engineering... There is the possibility that as an accident, a side-effect of such research, some quite new and virulent micro-organism might multiply to an extent with which we are not able to cope. As a consequence, the Medical Research Council in Britain... recently supported a six-month moratorium on research in that specific area while the matter was studied more deeply and new safeguards drawn up.

It is conceivable that machine intelligence research could at some future stage raise legitimate concerns of that character. If that ever happened then I would certainly support such a 'holding operation'.