Explain to me why it is wrong to lose more than 5% of your BR in one day. I dont mean say, "BUT I READ IT ON THE INTERWEBS", I mean actually go through why it is bad bankroll management + the implications it has.

If we have a large enough BR for the stakes we are at (say 20-40BIs for example) what is wrong with losing 5% of our roll if we are willing to drop down stakes when we fall below that necessary number of BIs?

If someone is playing 25NL with an $800 BR (35 BIs) and loses 2 BI, ie $50, in one day, how have they done anything even resembling poor bankroll management?