It's still inappropriate, but considerably less so, both because a C-level officer of such a large company is likely to have security arrangements of some sort,

It's still inappropriate, but considerably less so, both because a C-level officer of such a large company is likely to have security arrangements of some sort, and because a C-level officer has at least some influence over the policies of the company in question -- the CEO, of course, most of all. That said, there is a qualitative difference between showing up at the guarded front gate of a CEO's mansion, and showing up on the ordinary front doorstep of a rank-and-file employee's two-story house. The former can at least be said to "go with the territory". The latter verges very closely on an imminent threat of bodily harm; the whole point of such action is to demonstrate to its victim that he and his family are not safe anywhere, not even in their home.