What people are afraid of isn't Google having a negative effect by lack of motivation or technical competence, but the opposite. That Google will be very successful in doing what Google think is important while not taking anyone else's merit, interest or concerns seriously.

Being excited and not seeing a problem isn't so much reassuring as what people are afraid of. If you do end up being wrong and Google does gain too much influence from the perspective of someone outside of Google not only would you probably be getting a promotion but also be in a better position with more influence yourself since you are a part of Google.

So unless you are specifically convinced that what people are concerned about won't happen, which would be pretty hard to argue unless this activity differs substantially from others at Google, your comment doesn't really say much. As it doesn't speak to anyone else's interests.

Google has been a contributor to LLVM for about 10 years, and a major contributor for most of that time.

At no point have they tried to force something into LLVM that goes against the wishes of the community. They have always worked with the LLVM community to improve LLVM, and LLVM has benefited greatly from Google's contributions. I expect this project to be no different.