OD in front of a JVM?! Definitely not required.
Oh c'mon, man. This is such a blanket-statement. Of course it's needed when it's needed. Most amps gain something (pun not intended) when you put something in front. They behave differently. More sustain, response, tightness, etc..
The JVM as well. You'd turn down the gain on the amp anyway.
And for certain genres you DO need one. For the real heavy stuff, say Meshugga just to name one easy example; you won't get that aggressive attacky "plink" when palm-muting without one.
If you feel you don't need one (wonder if you even gave it a try in the first place ), good. More power to you. But sounding as if you're speaking for everyone with a JVM (or any amp for that matter)? Not cool
And no, not trying to start a fight. Just amused how some ppl keep claiming the same baseless thing over and over again.