How can you NOT kill the ball? It is under the control of the offense. If someone asks me why I killed the ball, I say, "Because it was under control of the offense".
If you don't kill it, what happens if he holds onto it for a second or two, then drops it, and then catcher (who had to travel a few more steps than he would have otherwise) boots it when picking it up and BR successfully takes 2nd base? Obviously the play was affected by BR. Can you retroactively call interference? No - because interference is a dead ball at the moment it happens, and you didn't call a dead ball.
What if, instead of handing it to the catcher, he lobs it to the pitcher. You killing it then? No? What if pitcher flubs the catch and boots it, and BR heads to second?
You even say... "Now if the BR decides to do the LL play and head to 2nd, guess what? He gets an assist on his own put out!" What if he's SAFE?!?!?! He "assisted" his own advancement. That is, to put it bluntly, WRONG.
You CANNOT leave this play live - anything that happens after BR picked up the ball is tainted by that act. Nothing good can come of leaving the ball live here.
And even though Tee was disqualified from responding by the original poster
, I'm curious to see if he agrees here. (Although he may not comment at all, as we started in boogerland are rapidly approaching TWP-land).