In some people's opinion, it may be wrong and offend them to call them civilians, though by definition, they are.It is wrong coming from a civilian Police Force.
In some other people's opinion, them being either police, civilian, or having been both, there is nothing wrong with that use of the term...kinda like a lot of other things here...we get to have our opinion, but not control others'.
Both military and police people often refer to clothes not their uniform as being "civvies"...no offense meant and I've never seen anyone take offense...but then I haven't seen everyone.
As if we didn't have enough to pooch our lips out at already.