I think both sides make good points in this debate. There was obviously a house here once and now it is only used by dogs, wildlife, and children in an area of poor levels of green space (not that this little patch makes up for a lack of local park). This point is actually about the furthest from a local park in SE23 (0.8 miles on foot to Horniman, Blythe Hill, or Mayow).
If this site is to be built on then why not also build across part of the entrance to Rojack Road, allowing for walking/cycle access only?
And the drawing does suggest that the rear garden would be rather small. While there are minimum guidelines for size of outside amenity space for families, no such requirements are needed for autistic adults (although it is generally recommended by other organisations)
Building on this small patch of publicly accessible green space will help preserve local car parks in the immediate vicinity which could otherwise be under threat from development.
There are loads of other sites in SE23 owned by Housing Associations that could easily fit a few flats with suitable amenity space, rather than trying to squeeze them into this spot. Fortunately we have a planning process that will look at the merits of the application when more details are provided. But it is worth considering the merits of this specific development rather than making it a general competition between dogs and people with autism. And it is worth consider which sites could be best to develop in a variety of ways, rather than assuming nothing can be changed from the street planning devised by Nazi bombing (I assume that's why the house is missing).