Over a database of videos they don't own? That changes rapidly in ways they can't control?

I don't think it's a bad suggestion, though their plan is most likely to influence people to complain to Google.

Same as politics, you want a maximum of people to be convinced by your idea/opinion/etc to make it happen faster. If you build your idea it might be great but if no one is convinced of it it won't work.

Mainly, because most people won't be exposed to it. They will be exposed to the Youtube's one and the effects over the majority are those that matter for the goals of the study.