This is a sneaky trick that people try to pull occasionally. They'll say something while I happen to be present (either physically in person or virtually by adding me to an email conversation) and see what my reaction is. If I don't say anything, then they assume that I agree with whatever it is they said.
Just to make it official: Just because you say something in my presence and I don't raise an objection doesn't mean that I agree. I can usually tell when people are trying to pull this stunt and I refuse to play along.
I see the same trick being played in the comments of this web site. Just because somebody posted a comment and I didn't post a correction doesn't mean that the original comment is correct.
On the other hand, the incorrect comment is archived on my Web site, which for many people implies some degree of approval, and which means that when people goes searching for a solution to their problem, they are likely to find the incorrect recommendation on this Web site, by virtue of the fact that it is ranked reasonably well by many major search engines. Did I just inadvertently help steer somebody to a wrong, possibly harmful, solution? Or is that not my problem?