Its true that sometimes old churches (often the newer ones, e.g. Victorian) become damp, crumbling and unsafe ... andwhat else can you do except demolish (and hopefully start again ?) In many cases, the congregations have dwindled away to no people at all.
But graves are, IMHO, another matter ... some years ago we had to put in a septic tank in the churchyard, and this meant disturbing some old graves; this had to be done with a Home Office license, by approved persons or contractors, and the remains we found were reburied with dignity elsewhere in the churchyard.
I wonder if the builders in this case are aware of these regulations?
HOWEVER, its as Stoney says ... 'church' can be anywhere; its not the building. 'Church' can be in someones house, a school room, a hall, or even the pub !