I have updated my respect for MIRI significantly based on Stu Russell signing that article.

If you don't think that MIRI's arguments are convincing, then I don't see how one outlier could significantly shift your perception, if this person does not provide additional arguments.

I would give up most of my skepticism regarding AI risks if a significant subset of experts agreed with MIRI, even if they did not provide further arguments (although a consensus would be desirable). But one expert does clearly not suffice to make up for a lack of convincing arguments.

Also note that Peter Norvig, who coauthored 'Artificial Intelligence: A Modern Approach' with Russell, does not appear to be too worried.