the problem is the contradiction in his powers.
if he's able to so easily grab bullets and send them flying to the opposite direction, then he should be completely bulletproof
yet there were numerous instances when he was apparently vulnerable to bullets and other weapons.
it makes no sense

The argument could be made that Barry moving at the velocity he does is able to exert enough force in that moment on the bullets to counter their momentum and reverse it. By grabbing it he'd need to exert enough force to reduce their momentum to zero, and while it wasn't made obvious he COULD theoretically transfer his excessive reserves of kinetic energy to the bullets once he turns them around, which would give them enough velocity to continue in the other direction.
I mean even I only slightly understood what I just said, but if nothing else it proves you could BS any kind of explanation for this super-speed sci-fi stuff if you really need to. Personally I don't really give a crap when it comes to the Flash, as even in the comics a lot of his powers don't make any sense (infinite mass punch springs to mind).

he doesn't simply turn the bullet though he moves it much faster than the speed it is shot from the gun btw in a loop till it aims back at the shooter at which point he releases is, to us looking like he's stopped it dead on because he's slowed it back down to it's original firing speed at which point once he releases it then it appears motionless again.
I think it kind of works but I'm not sure, but he didn't simply just spin the bullet around like he just twisted it around he made a point of altering it's trajectory back into the guy shooting.

no, in days of future past quicksilver simply deflected the bullets sideways, the bullet still traveled to the same general direction.
here, barry takes a bullet , spins it around 180 degrees, does NOT visibly push it toward its new target, just lets it go, and the bullet just flies to the new direction.
it's as if they thought the bullet would fly toward whatever direction its tip is pointed at.
that would only work if it's propelled by something from the opposite end.
otherwise it would maintain its original direction even if something spins it around.
it reminds me of the movie Wanted in which they could get bullets to fly in circles by spinning the gun at the moment it shoots out the bullet

that scene seemed to be taken right out of X-Men: Days of future past, where the bullets did the same thing

like men in black are your standard cop

Barry is a smart cookie.
You don't become a forensic scientist for the police if you can't understand that other people in law enforcement are just doing their jobs.
He's had guns pointed at him before, when he wasn't as known.
he didn't redirect any bullets back to them.
Because they were doing their jobs.

Barry did not know they were just doing their jobs, they were a mysterious threat to be dealt with.

Alsothese men were just doing their jobsAt what point did Barry find it alright to let a random person take a bullet, when he's so quick to save Oliver and Diggle?