He claims Humans consuming Splenda will kill off 50% of their ‘gut microflora’ 
In the study, Splenda sweetener, which contains 1.1% of actual sucralose and the rest fillers, was administered to rats at Splenda dosages that contained sucralose at 1.1-11 mg/kg (the US FDA Acceptable Daily Intake for sucralose is 5 mg/kg). Now relate this amount to a human.
Assuming that the same effects would be observed in a human, and that follow-up studies get similar results, how much Splenda is this for a 60kg person, or a person that weighs only 140 pounds? To get the minimum you need to repeat this 60 times, which comes out to be 60 packets of Splenda and the maximum is 10 times that at 600 packets a day 
Now compare this to me at 91kg and my favorite drink mix contains 5 packets per liter would be 18 liters minimum and 180 liters maximum a day 
I drink 3 liters so I think I’m safe 
Here is the study that was funded by the Sugar Association 
Splenda alters gut microflora and increases intestinal p-glycoprotein and cytochrome p-450 in male rats.
https://www.ncbi.nlm.nih.gov/pubmed?cmd=Search&term=splenda+and+Abou-Donia+and+El-Masry+and+Abdel-Rahman+and+Schiffman&doptcmdl=Books
Is Splenda Inadequately Tested and Unsafe?
An Expert Panel conducted a rigorous evaluation of this study. In arriving at its conclusions, the Expert Panel considered the design and conduct of the study, its outcomes and the outcomes reported in other data available publicly. The Expert Panel found that the study was deficient in several critical areas and that its results cannot be interpreted as evidence that either Splenda, or sucralose, produced adverse effects in male rats, including effects on gastrointestinal microflora, body weight, CYP450 and P-gp activity, and nutrient and drug absorption. The study conclusions are not consistent with published literature and not supported by the data presented.