U-boats...good strategy or not?

I think that the idea of using U-boats was a good idea at first.  The Germans needed a way to defend themselves against the British blockade.  While many blamed the Germans right away, I think that if those people were in that position, they would have done something similar.  However, self-defense can only be taken so far.  When the Germans started attacking merchant ships, things got way out of hand.  Usually, the attackers would have to search the ship and cargo before sending them back.  They would sometimes pay for the cargo as well.  In this situation, though, the Germans were simply sinking these ships without any confrontation.  This, in my opinion, is very wrong and inhumane.  At this point, they were simply out there to kill.  Things were taken to extreme measures when they sank the Lusitania.  Although they did apologize, I don't think they were very sincere about it.  They only apologized so that the Americans wouldn't get involved in the war.  I think that things are like this in our world today.  People apologize so the other people will forget about it and hopefully not get involved.  Also, people only try to get involved when there is some benefit or detriment for themselves.  For example, if there weren't Americans on the Lusitania, would America have cared as much?   For example, America is getting involved in the middle east because there is oil there that we need.  If there wasn't oil, would anybody care?