There;s probably a lack of sound evidence because there have been no long term studies on it like looking at the impact on a specific lake over a long time period and covering ALL variables. Here are a few links describing some studies. Notice how not all variables are accounted for like tournaments and more fertile vs. non-fertile waters.
http://www.ms-sportsman.com/details.php?id=1451
http://www.bassfan.com/opinion_article/1360/science-and-the-impact-of-bed-fishing#.Vz8Cu_krLbg
But think of it this way. If you're fun fishing, you catch a fish off of a bed and release it right away and it goes back, there's less chance of damaging impact than a tournament where 50 fish are taken off of beds for 7 to 8 hours leaving them wide open to predators. Also consider the number of bass that end up actually making it past the egg stage vs. the number of total eggs laid. Then consider multiple tournaments over the spawn season. The risk at least is pretty obvious.
You could argue for article #1 where it only takes a few bass to populate a body of water but then you also have fishermen that fish beds and simply take the fish home to eat.
While it's inconclusive, I'd rather not take that risk and tournament bed fish. I've done it, but I think it's pretty dumb. 15 boats all pounding beds vs. finding patterns.
I was bed fishing from shore this past weekend because I found nothing was biting if I casted far out. That said, I came across a video by this kid Tyler (video https://youtu.be/NXfDaWXPnIA) and I can't remember if it was this particular video but he noticed a something when both the male and female are near the bed. The kid puts GoPro cameras in the water and you get an awesome view of what the fish do to our lures.
Basically, the male plays defense while the female swims circles around the bed. In one of his videos, he drops a lure onto a bed and as the female notices it and goes to bite, the male actually snips at the female to keep her from biting the bait. Most likely it's because the male just wants to get down and tap that (b)ass but it was still pretty cool to see.
So when I noticed a male and a female (female was HUGE) guarding a bed about 5 feet from the shore, I decided to experiment and tossed a senko onto the bed. What do you know, the same exact thing that happened in the video happened on this bed. The female caught sight of the worm, went to bite it and the male was like NO and snipped at her. She quickly swam about 5 feet away, and he just stared at the worm for about 30 seconds. I twitched it a couple of times to get his attention again and he grabbed it as if to move it off the bed, and instinct kicked in so I set the hook. Got him out in 5 seconds, perfect hookset, popped right out, and placed him back into the water. He returned to the bed in about 30 seconds like nothing happened.
From that point on, I will not be sight fishing bass beds. It did have an impact on me, both at how easy it was, and the fact that I don't want to disturb what could potentially be a future bass by c**k blocking the fish. I'd much rather look for cover or fallen trees and find that post-spawn bite.