If you're going to counter someone's point y claiming to be an expert, you really need to link to some credentials. If you're not going to do that then linking to some research disproving the parent comment would also be useful. Without any of that it's just an untrustworthy claim and doesn't add to the discussion in anyway.
I was looking at that and it seems to be more of an opinion survey of university professors of economics about a bill that had trickled-down as a part of it, rather than a formal journal entry.
> Tax policy appears to have little effect at the margin on GDP growth in OECD countries.
This idea did come up repeatedly though, so I assume it is a common-enough belief in economic circles.