I dont' bass fish, but, doubt a 7 weight would not be enough rod
For a lot of open water bass fishing a 7 wt is fine. I've caught many hundreds of bass on a 6 wt. which will easily handle the size bass most of us hook. I've landed Stripers up to 30 inches on a 6 wt too.
However, I agree with Chuck S. I fish with an 8 wt much of the time & a 10 wt a lot for bass. I do this for 2 reasons. 1) There is also the possibility of hooking into Striped Bass in most of the places I fish, and 2) even a 2 lb bass is tough to get out of some of the tangles when it's wrapped up in 3 lbs of vegetation. Not ideal conditions for a 6 wt. I still use the 6 wt, just not in the same manner as the heavier rods.
I'm one who feels that bigger is usually better when it comes to fishing for LM bass & the size flies used. For many years, I fished with smaller size flies, and caught plenty of fish. But, once I began using bigger flies, as well as bigger lures when targeting bass, I started catching more larger size fish. I do however catch less fish than I used to, but I'm fine with that. Most anyone who frequently targets the larger size bass will tell you that they get skunked a lot, but the ones that they do catch are usually of a better size.
As I have said, in the waters I fish there is also the possibility of hooking into Striper's and I've caught enough LM bass on big saltwater lures while targeting Stripers, to be convinced that I should be using larger offerings for the LM Bass.
but why is it that we can fish for 20+ inch trout with a #14 nymph, but feel that a LMB won't move for anything less than a squirrel's tail with a couple of huge hooks woven in?
Because they are 2 different types of fish. Their physiology is different. Even large trout will often feed on small insects, but larger bass are more inclined to feed on larger prey. Both are a product of their environments. That mouth on a LM bass is large for a reason. A 6 lb bass can almost swallow a 20 inch trout. It's been my experience however, that even larger Smallmouths in stream environments may still be actively feeding on insects that may be present. I think most predatory fish are opportunists & will take advantage of whatever is available to them in the greatest numbers.
Yes, there are certainly times when larger fish will eat the smaller offerings, as nothing is guaranteed when it comes to fishing. I have frequently used ultra light spinning tackle for targeting bass, as I've found that the lighter lures spook them less, IF, they have been fished hard. Some of the waters I fish are quite shallow & are used for local bass tournaments, and that extra pressure can change how they accept a lure. I've not found that I need to switch to lighter fly rods, as even larger flies will not land with the same impact as lures. But, I'm sure in some places, it could be beneficial to go lighter even with flies.
The rod recommendations are varied, and all good for the reasons each person has stated. It boils down to what you feel will best fit your fishing, because you're the one who has to be satisfied with the choices you make.