They're confused on purpose. If you explain anything to them, they'll reject it so they can continue to be "confused".
And if you use examples of any Star Trek from 1966 to 2005 to back you up, they'll reinterpret it so they can continue to bash whatever Discovery (or Picard) is doing. Doesn't matter if that reinterpretation means they're misrepresenting Old Trek. That's collateral damage if they accomplish their objective which is to "Bash any new Star Trek at all costs."
There are surprisingly more people who take great exception with the argument that "Star Trek has always had these flaws" than I ever would have thought possible.
I think it's weird thing to bristle at. Sure, I can accept and acknowledge PIC and DSC have their flaws, but why is it so wrong to point out, particularly to a franchise fan, that the flaws they are talking about (in this hypothetical example) have been there time and again in other/all iterations of Trek? It just seems odd to get pissed about. To me, it seems like a completely valid and sane element to engage in discussion on.