To be honest, I think it is an overreaction to be unable to handle the occasional panty shot. It seems like they are projecting their own morbid fascination with teenage girls onto everyone.
The fanservice added a nice touch to the overall experience. You had horror, wholesome, and ecchi in the same manga. That is a somewhat novel combo these days. Chained soldier has a very different vibe.
There's nothing wrong with ecchi, but it can definitely be a bit of a fly in the soup for a lot of people, especially with manga and anime. And there's nothing wrong with that, either.
I like fanservice in a lot of what I read and watch, but I've disliked it in just as many things. I don't think you can make a blanket statement along the lines of "these people are just repressed prudes" for being unable to look past it when it is present.