I mean this rule is equally awful as it is incredibly valuable and there really isn't a way to change it without ruining the balance (at least in my opinion).
For one, 2.1 makes being traitor a looooot easier. My average T round consists of me shooting people in the head and saying they tried to shoot me so i can't be kosed for it. This is obviously not a good thing and it just adds to the whole "i know they're the traitor 100% but i don't have solid proof so it would be rdm" thing which plagues anyone who plays TTT. Yes, you can kill someone if they give a shit reason but when its as easy as going "oh yeah that guy tried to shoot me but missed" it's pretty impossible to find a discrepancy with what they're saying. Even if they give a flimsy excuse, its still very possible they'll report you for rdm and try to get you warned, and are you really going to take that risk?
But at the same time, it's a sort of necessary evil. I mean i've played TTT for quite a bit personally and anyone who has played it for at least 5 minutes can tell you how much shit you go through with people rdming you because "he killed an innocent." As a staff member for around 4 months now, i've seen countless reports of people just going up to someone and shooting them in the head because they killed a mass rdmer and weren't given time to explain. If you take out rule 2.1 then what happens? If Little Timmy gets his right kneecap blown off by xxx_Kyle_xxx (completely random name) and is killed for getting revenge, what would you do? If you take out 2.1 then he's dead meat because he killed an innocent even though he didn't do anything to deserve a kos.
So yes, this rule is complete and utter bullshit, but it's also one of the most important rules in the game. If you removed it, i can guarantee things would be worse off.
BBCode