Personally, I don't really need a safe injecting space - I own my own home and have a pretty stable lifestyle, but again, I can see how for other addicts it would be incredibly helpful. Again and again, as seen in other comments, it can be seen how despite objections these places provide an objective positive benefit to society.
What medically administered heroin does is allow people to get that time back so they can rebuild their lives. Once they see that things are better, they become more successful when finally coming off of it. Even if it takes forever, they are still productive members or society instead of a drain.
A methadone maintenance program will gradually increase the amount of methadone prescribed, while the user reduces the amount of heroin they take, until the user is 'stable' and no longer using heroin. After that I certainly would like to then stop taking methadone too, but in some cases the maintenance can continue indefinitely and it would still be considered a net positive outcome...
But let me be more clear about what I mean by "death grip".
When someone cares so much about a drug that it becomes the focal point of their lives, where they become so utterly ruled by the object of their addiction that friends and family and all else not the drug become secondary fixtures in their lives, then they have become the walking dead and are very much in the death grip.
I have seen it with friends. Some are still breathing, some are not.
Sure people on medical grade heroin regimens can continue to exist, but the drug will kill them inside nonetheless.
Revitalization is possible of course, but it is exceedingly difficult.