The product of a protest is just the protest. It only means that a number of folks feel strongly enough about something to put their leisure time on the line. It doesn't much matter who got the word out to them that there would be a big rally at some location at some time. [assumes the protesters were not actually paid to be there]

A scientific study [I shouldn't have to point this out to you] is supposed to determine the validity of a hypothesis. In order to do that it requires impartiality in its design, in its execution, and in its collection and reporting of the resulting data.

Intellegent people usually question impartiality when the study is funded by folks who have a strong interest in the results coming out one way or the other. Good grief, why wouldn't you?

On the other hand, questioning impartiality DOES NOT INVALIDATE THE STUDY. It just means that folks should scrutinize its results that much more carefully.