Justified Sinking?

[Kaptlt.Endrass]

So, hello fellow captains! Long time since I've posted here, but it's kind of nice to be back.

Down to business, however...

It's June 1941, and I'm out patrolling the mid-Atlantic, around Grid BE46. It's been a fairly unsuccessful patrol, with only a single large freighter to our name. There's been several ships that we've seen, mostly neutral, others not worth catching up to to engage.

Finally, the 23rd of the month, one of the men spots a merchant ship headed towards us. Closer inspection reveals it to be an American tanker, and I almost give up on it.

However, continued observation makes me suspicious, and I run some measurements to see that the tanker is moving at a speedy 17 knots; much more than any other neutral ship we've encountered so far. Believing the ship to be making an attempt to run the blockade around England, we set up to engage with the deck gun, sinking her with somewhere in the range of 25 shots.

Now, I know that the Americans were still neutral at the time, and typically try to avoid hitting their ships until they enter the war (which makes convoy attacks a pain). But would you say that there was enough justification to sink the tanker, given the circumstances?