Why is Crying-It-Out bad?

[UnityMom]

I'm at my wit's end, with no endurance left, very little patience, and hopelessly frustrated.  I've lost all sight of my original wonderful intentions regarding sleep training, and I'm having a lot of trouble remembering why I used to be so sure the CIO was a bad thing.   

Someone, please help!  Please remind me -- why is CIO bad? 

Thanks,
UnityMom
(first time mom to 5 month old son (textbook baby) on 4 hour easy.)
8am:  wake up and breakfast (similac advance and cereal)
10am - noon :  nap (in theory, reality is 20-45 minutes, then the rest of time me desperately trying to get him to sleep again)
noon -- bottle and jarred baby food
2-4pm -- nap (again, works in theory, but not reality)
4pm -- bottle
5:30 -- 30-45 minute cat nap (unless by some miracle he took both 2 hour naps.  ha!)
7:30 -- bottle and bedtime routine
8pm -- night night
8pm to 8 am -- supposed to sleep thru, but we have 6-17 NW a night!

tell me, again, why i can't just put in earplugs and let him scream himself into a stupor?

[Lana]

Here is a link as to why it is bad

https://babywhispererforums.com/index.php?topic=63839.0

Trust me when I tell you that I know what you are going through. I have taught two boys to sleep now and it is still pretty fresh from round two. 

Have you ruled out teething, developmental milestones and sickness.  You are nearing an age where there will be alot going on. 

[Jaime]

also... just another thought... he is still pretty young for solids; maybe one of those is affecting his digestive system & making it hard for him to settle down??

the NW are probably due to day sleep being so scattered, so definitely keep plugging away at the naps.  i also remember being in the trenches of sleep training - you do come out of the other side eventually!