First, I will say I respect the work that anyone puts in, and a win is a win.
To answer your question, any ammy title is only as "legit" as the competition available that year. In the Gloves you may have to fight 3 bouts to become champion (Friday, Saturday, Sunday). You may have to fight 2 bouts. If the comp is low on contestants in your division you may only have 1 bout to win the title, even in Golden Gloves.
The level of difficulty all depends on who enters. Also, someone may not have a record but they've been fighting, sparring, and hanging out with boxers for a long time. They can enter these competitions, and present real problems for those who may have only a couple months experience prior to entering the tournament.
The difficulty is all relative. Silver Gloves is for kids, I believe it is under the age of 16 (don't quote me---that's off the top of my head). I know a kid who won Silver Gloves, and he is a little animal. He is legit, and the work he put in to winning was legit. So yeah, it's all relative, situations differ.
I thought Silver Gloves was just a regional championship, but seeing footage online and looking at Ringside's website, I guess you can go to Nationals in that category. You're friend is no slouch. Good on him for his success.