It's not actually what you think. He was arguing that as a result of mandatory minimums defense attorneys like him would have no other choice but to rigorously go after child victims in order to ensure their clients get a fair trial. I think that his choice of demonstrating that point was wrong, however, I happen to agree with his general point.
Pushing mandatory minimums means that cases that could be resolved in plea deals will have to go to trial and force the child to testify because such laws tend to hamper most judicial discretion. The laws also mean that people accused of non-violent acts could face the same sentence as someone who violently raped a child. The laws may also apply to juveniles who are charged as adults, meaning that 10-year-olds could be in prison for the rest of their lives for first-time offenses.
The point this attorney made a few days ago on MSNBC was that nearly all the prosecutors in that county were also against the law. The reasoning behind their rejection is probably because a lot of offenders are willing to accept plea deals, but usually not deals that require 15 or 25 to life. So, instead of being able to offer 10 to 15 years with probation, prosecutors would be forced to go to trial and place the victim on the stand and make that child recount their abuse. If the child cannot take the pressure, then the child might refuse to testify or might breakdown on the stand.
The laws are just not very good laws. This defense attorney could have said that in a less offensive way, but his general point seems valid.
Every day I die again, and again Iím reborn/Every day I have to find the courage/To walk out into the street/With arms out/Got a love you canít defeat/Neither down nor out/Thereís nothing you have that I need/I can breathe/Breathe now - U2