std::atomic to what extent?

In the C++ Seasoning video by Sean Parent https://youtu.be/W2tWOdzgXHA at 1:17:12 when starting to talk about “no raw synchronization primitives”, he brings an example to show that with raw synchronization primitives we will get it wrong. The example is a bad copy on write class:

template <typename T>
class bad_cow {
    struct object_t {
        explicit object_t(const T& x) : data_m(x) { ++count_m; }
        atomic<int> count_m;
        T data_m;
    };

    object_t* object_m; public:
    explicit bad_cow(const T& x) : object_m(new object_t(x)) { }
    ~bad_cow() { if (0 == --object_m->count_m) delete object_m; }
    bad_cow(const bad_cow& x) : object_m(x.object_m) { ++object_m->count_m; }

    bad_cow& operator=(const T& x) {
        if (object_m->count_m == 1) {
            // label #2
            object_m->data_m = x; 
        } else {
            object_t* tmp = new object_t(x);
            --object_m->count_m; // bug #1
            // this solves bug #1:
            // if (0 == --object_m->count_m) delete object_m;
            object_m = tmp;
        }
        return *this;
    }
};

He then asks the audience to find the bug, which is the bug #1 as he confirms.

But a more obvious bug I guess, is when some thread is about to proceed to execute a line of code that I have denoted with label #2, while all of a sudden, some other thread just destroys the object and the destructor is called. So, the first thread will encounter a deleted memory location.

Am I right? I don’t seem so!