Babies definitely do cry for a reason and sometimes that reason can be that they are just too tired and want to sleep. If gentle methods of getting them to sleep (e.g. feeding, rocking, singing, co-sleeping etc.) aren't working then surely you should try something else, rather than have them suffer from lack of sleep. When Maria was at her worst she was suffering, she needed to sleep more but couldn't. Nowadays even though her sleep is still shit, she gets enough and isn't suffering (as she is generally happy throughout the day and not grumpy like she used to be when she was tired all the time)
I dunno, whats worse? Letting your baby cry or letting them suffer through lack of sleep? They both have negative effects on the child, you just have to figure out which is the lesser of two evils.