I'm a machinist by trade and work for Pratt & Whitney refurbishing jet engine parts. These include military as well as commercial jets. Most of the repairs are done using welding, plasma, or nickel and they are made up of alot of MIM parts , yet they still manage to withstand ALOT more abuse than any firearm ever will. Even the 718 inconel parts can crack and have vioids from heat treatment.
I think it's ok for your firearm to have mim parts on it, just not in the areas you consider important. Like JD said, the problems comes from voids which you shouldn't have if the part is forged and heat treated right.
The manufactures should have x-raay and fluorescent penetrate inspection to catch those mistakes.
CZ's have mim parts and I have never heard of or read an issue with them.
I also agree with not spreading the rumors. Many people will read or watch on youtube someone spilling out information as if it were fact, when they actually have no idea what they're talking about. Remember the guy who was showing people how to unlock the slide of his xd by slamming it down on a table, "this is how you fix this." ROFL!!! I wonder how many xd bangers that created?