I'll add a recent backstory to illustrate my mindset on this.
Week 8. Team I was facing in my biggest money dynasty league and what I viewed as one of the main contenders for the highly coveted top two seed had Tee Higgins in his lineup. This was the week that Tee got hurt in practice on Friday. I saw it about an hour before kickoff he still had Tee in his lineup, assumed he'd change it. Checked back with about 15 minutes to go and saw it was not changed.
Not only was I not even considering telling him, but if he took a goose on Tee combined with some mid performances from two key players he had going in the Thursday Night game I was strategizing around it with my lineup calls. With about a minute to go before lineups locked I made sure he left in Tee, made my lineups calls accordingly(which were mistakes but don't want this to get to long winded)
A little over an hour after kickoff I saw an email that his lineup had been changed by the commissioner and Tee replaced. I was not pleased to see a lineup switch over an hour after they locked and no one bothering to explain it to me. Caused a lot of rancor in the league. Story changed a little over why it was done over and hour after kickoff but loose version of the story was my opponent says he's was in an area he could not access the league, but was able to send an email to the commissioner asking him to pull Tee. Commissioner says he got this email a few minutes after lineups locked, but before kickoff, but was on a flight and could not make the change until he landed.
Maybe some of you would have said that's cool. Not me. I don't even care to examine the validity of the story. Could be 100% accurate, don't know or care. You got a deadline to get your lineup in and that's on you is how I see it. I fought this tooth and nail to have Tee removed from the lineup and really caused a lot of rancor in the league, which I hated to do, but felt sure in my convictions.
So that's how I roll. I expect people, especially in highly competitive leagues were decent money is involved, to be responsible for their own team*. I play to win, expect my opponent to do the same and if you are not up to the task I'll try and use it to my advantage.
*if I got reason to believe someone has a health issue to them or their family, stuck in a natural disaster, things like that I would not feel this way. Just wanting to make that known there are instances I would allow a change, inform the owner if I knew he was in this predicament, etc, etc, but in the absence of something like that, hell no.