Not sure what to say other than that is full of bad information.
There is no data anywhere that would support or purport the use of Benadryl for snake bites. Benadryl is an anit histamine, snake bites have little to nothing to do with histamines. The venom is a hemotoxin with enzymes that cause tissue destruction, none of which are histamine mediated.
There is only one treatment that is undisputed and scientifically proven, anti venin. It neutralizes the toxins in the venom. The biggest issue is cost, it is expensive to treat with a sufficient dose to be effective.
Not much of anything he says in that article is correct.