How about if you use "a brick and mortar store to physically compare products first", you buy the item in the brick and mortar store. They already shipped the item, so you are not hurting the environment further by wasting energy getting another one to you. If everyone shopped at "brick and mortar stores" this way, they would close. People in your community would be fired, and you wouldn't be able to compare products personally.
Obviously not a big deal as a one-off, but if this is a consistent shopping habit I would really hope you reconsider it.
I don't actually shop that way, I take my chances based on Amazon ratings (not a hard thing as I buy mostly electronics and media). My only direct concern is that he keeps Amazon prices low for my own benefit.
I don't really see the point in artificially trying to keep business models afloat that can't compete. If anything, it's harmful to the free market. It might warm your heart a bit, but the overall benefit to society is to cast your vote (your $) for the most efficient business method.
If you use Amazon exclusively then no problem, all is good.
My only concern was that the advice artificially keeps a business model afloat (Amazon) that relies on the existence of brick-and-mortor stores. Its like people using the local hardware store for advice then buying all the parts at Wal-Mart.
What's hurting the brick and mortar store is not the "going in to compare items" part, but rather it's the "buying on Amazon instead of from the local store" part. You may as well say, "If everyone bought online instead of at the store the stores would close."
Obviously not a big deal as a one-off, but if this is a consistent shopping habit I would really hope you reconsider it.