This should never, never happen. Top of the respect list are those that serve. I only did the weekend playground, so I don't qualify.
As a thought and idea, what if any exservice are sleeping rough they have a particular marker or way to identify them. If they did I would make a point of giving or supporting them directly. I met one guy and to double check (London) I said what's your service number, immediate reponse rattled off, £20 help (all I had at the time).