Really? You sure about that?
Because the V2, and I checked this, had roughly a 50% chance of hitting an area 17km across at a range of 300km. Now this is fine for a city. But if you're launching at an Air Field your chance of hitting anything important is going to be minute at best. And should you fire at a port, you've got a 50% chance that it falls into a circle which is 50% water. And even then the port facilities are going to be in a fairly narrow line along the shore. So once again your chances of hitting an actual port facility with a V2 are going to be minute. Instead you're rockets, assuming they hit land at all, are likely to fall into the city. If you're going to bombard a city, might as well make it an important one like London. Now, you probably could have got a V2 to fall with a certain degree of accuracy into a D-Day staging camp as they were the size of a city. However as Hitler didn't know they were there for the most part it's a moot point.
The Blitz proved that the British wouldn't crack bombardment of their cities. Why would a far more limited rocket bombardment have a different effect? Yes, obviously the intent of attacks against cities is to hurt the morale of the populace.
But if Hitler had the capability of modern Cruise missiles, he wouldn't have fired them at apartments in London.
Lastly, purposeful targetting of civilians was historically a militarily sound option in certain situations. Knowing that you're failure to surrender would result into the massacre of an entire city was sometimes enough to convince defenders to lay down their arms. And fear of retribution meant that in almost all cases of sieges the defenders surrendered as soon as the walls were breached.