As much as I appreciate this source, it is not peer reviewed or even published. It looks like a student article. I therefore cannot use it as a credible source. I'm sure you understand.
But onto the points brought up.
Once again, divergent lineages are used in defense of this argument. This is bad practice and should be discouraged in any scientific field. You can bring them up, sure, but they cannot be used as a defense for the non-divergent lineages.
The canid group is highly adaptive though. That's why we managed to domesticate them. That's a given. Problem with this research is that it has no attempt to look at the actual feeding habits, only circumstantial evidence like stomach content. This evidence is essential, but ultimately incomplete without evidence of how those contents were infested. The only evidence of foraging here is if feral dogs. This is fair research but lacking.
For example, many predators consume the stomach contents of their prey.
Also, the aspect of environmental pressures is ignored. Any animal, no matter what their diet, may be forced to try a multitude of different foods during times of drought or famine, etc. so it's understandable that an extremely hungry dog would eat whatever the hell is available, no?
Thanks for another lesson on dentition. Like we needed it after this week of comments?
And finally, we end off with nutritional science which confirms that my kitty is an obligate carnivore and in an ideal environment my dog is too. My dog is more than capable of surviving on an entirely meat based diet, though there are numerous adaptations allowing them to survive with plant supplements, which is especially useful in difficult environmental periods.
So, even though I seriously question the scientific literacy of this community, often, and I try to increase this level, often, I'm still left feeling as if nobody is dissecting the badly done research that they use as evidence. Strip it apart and examine everything.
Thanks for the source though. Next time, use an actual journal article.