For those who do not know (or think you know): this is panic knifing.

By definition: You see people and your knee-jerk reaction is to clench the controller so you end up knifing (default) or going prone (tactical).  People often think that panic knifing is trying to knife someone at all costs. That is not panic knifing... that is just stupid. (lol)

On topic:  here are some suggestions

1 - Stay on tactical and never stop firing. Get yourself mentally aware that you are gonna go prone so be prepared for it, and adjust you aiming as your target is gonna strafe you.

2 - Practice hip firing. Once you are used to it you may stop clenching the controller as you are mentally programmed not to ADS.

These may or may not work.

I'm glad I'm not the only one to do that. I've done it a couple of times. I seem to hold down fire button but knock the right controller at same time so end up trying knife someone who is out of range. Makes me feel a right prat. Didn't seem to do it on all other COD games. Strange. Doesn't feel as though I'm pressing right stick and I don't hear a click either so don't understand why I do it.

I'm not heavy handed, it's the controller. This never happens on the 360 controllers, unless you actually press the R3 button. On PS3 controllers, I will not press down on R3, yet it will knife when I'm clearly trying to shoot.

Another example, when I play BF3, I always go prone when all I'm trying to do is flippin shoot. It's very annoying. I don't like tactical layout. And even if I did use tactical layout, I would look like a drop shot wussy all the time. When in fact I'm not trying to drop. The PS3 controllers are very sensitive on the sticks.

This happens to me all the time, but oddly enough, only when I use a dual shock controller because the sticks seem a little sensitive. This happened to me a lot on MW2, not so much on MW3 but it still happens. I've tried the tactical layout and just can't get used to crouching with the stick, though I guess that's how all the drop-shotters do it.

I was always pretty good at Halo on xbox so when I saw the PS3 controllers that were modified in the xbox controller design I picked one up and found immediate improvement in my overall game play just by switching to the controller. I have always felt the xbox controllers were more suitable for FPS games. I've never had any issue with the "panic knife" on the new controller so maybe that is something you could try.

Run tactical and learn how to drop shot. Problem solved.