I am not sure that "other people are jerks so we can be jerks back" is really a helpful argument. It kind of feels like the American argument that says "The only thing that can stop a bad guy with a gun is a good guy with a gun". Yes, DPS are frequently culprits in this, does this mean we want to arm tanks and heals with the capacity to retaliate?
Also, how many people on all 3 sides of this debate are going to pre-emptively strike bad damage dealers? In my, admittedly, exhaustive experience with PUGging in addon-enabled MMOs has shown that people doing low damage lashing at the tanks for not surviving adds and heals for not keeping the tanks in check occurs just as often as you see tanks preemptively vote kicking DPS because the first boss didn't go down fast enough. If the issue is really DPS wanting to know if they are measuring up then there are better ways to do it than making any failure publicly available.
Shaming people for being bad at their job doesn't actually help them improve. It only makes them more nervous.
I think the answer to tanks and heals getting flamed is regulation, not more fire. The commendation system is designed to incentivise more cooperation. The devs should focus there for eliminating hostility towards tanks and heals. The fact that tanks and healers are largely pacifistic at this point (though my sample pool is hardly representative) is good. As a DPS myself I think the answer is to encourage DPS to be less hostile.
If the driving issue behind enabling mods revolves around damage meters then I might suggest a different solution. What do you think would happen if SE decided to add a separate commendation that can only be given to PUG DPS? Greater scientists than I have already proven that the lower vitriol among tanks and heals can be linked to them getting most of the Coms. I think the hope of getting the commendation could help to alleviate the issue of harassing DPS better than giving tanks and healers a way to bash back.
In short, if the reason for damage meters is to check unruly DPS, the answer is letting them know that there are consequences for their actions and letting the know that those consequences don't have to be negative. These people are cruel because they need attention, lets give it to them.