A quick google search of “Monta Ellis Bad Defender” will turn up a host of interesting web pages. The very first link sends you to 2014’s annual feature by Tim Kawakami naming the “All NBA No-Defense Teams” in which Monta lands an “Honorable Mention” spot on the dubious squad. The second link finds you reading a fascinating rebuttal on NBA Reddit titled, “Why do people think Monta Ellis is a terrible defender?”
Both posts are mostly reliant on the good old fashioned “eye test” with a few hard-to-contextualize stats thrown in, supposedly offering some measure of argumentative support.