I feel like viewing photography can be considered spectatorship if it seen by people more removed from the nature of the object being photographed. 

War photos ranging from all time periods in history up until the present have one thing in common, intense suffering. When I look at an image of a battlefield from WWII I feel like a spectator since I am so far removed from that time and place. When I look at an image stemming from a war torn country in the Middle East in the present, I still feel like a spectator but also feel something more. I feel that this is happening now and there is possibly something I can do to help. I feel  like this is where the line is blurred between just being a spectator and something more . 

When the photograph instills a feeling that could lead to a rise to action or a sudden realization, you become more than just a spectator. You become what the photographer may want you to become. An active player, a contributor and someone who could possibly make a difference. 

Source:

I believe the intention behind the photographer's decision to take a photo of the homeless or other types of suffering dictates if it is bad practice or not. Of course if it is to mock them or to use them to their claim to fame then it is bad practice (reliant on moral compass). But if the intention is to raise awareness or tell a story then the photographer is an active participant in the possible improvement of those people's lives. If a journalist from a country experiencing turmoil in the form of war, or natural disaster is desperate to get their message across to other countries for aid, then them taking photos to send a message is far from being just a spectator. 

To answer the last part, I do not think it is wrong to be privy to those intimate moments. Sharing the knowledge with others and spreading awareness may be part of the photographer's plan all along, so, taking an interest would not be such a bad thing. 

I believe that people can be spectators up to a certain point. It is when the photo makes you feel strong emotions that make you act in any way that it becomes more.

Here is an interesting link to read about times photographs have inspired action.

https://www.nationalgeographic.com/photography/proof/2015/12/31/8-photos-that-inspired-action/