Walking into a hostel that you are not staying in for the sole purpose of using the showers to see naked men who are staying at the hostel is predatory behaviour.
You're definitely getting the wrong end of the stick (with me at least, I can't speak for everyone here). Any enjoyment I get out of seeing any naked men is going to be 100% mutual and consensual. I'm a 30 year old gay man that lives in Brighton, I can get laid whenever I want. I don't need to prey on anyone. I just enjoy that all male environment, and I don't see anything wrong with that. I'm not going to make anyone feel uncomfortable and what I'll be doing is no different to what hundreds, maybe even thousands of other gay men will be doing all over the city in various gyms, spas etc.
I'm only staying at another hostel because Generator doesn't have male dorms (same sex spaces unfortunately are dying a death at the moment) and on this occasion I can't stretch to a private room. But I have booked a bed and will check to see if it's all male and if so I might even stay there.
So I'm booked to stay there, anything I do will be consensual and non predatory... so what is the problem exactly?