To be honest I've been thinking this through because I did feel a bit mean spirited for sending him away. However I think I was irritated, not because he was a beginner, but because he hadn't even tried to get things sorted out properly (EG only 2 short lengths of rope on board). We've all had novices coming alongside and usually they are a little nervous, but at least they know what they are trying to do........it's just the execution of the manoeuvres that may not be perfect. We've all been there ourselves. This guy had no idea at all.
The other thing that I learnt was that hailing a boat before you come alongside is more than just courtesy; it gives the moored boat some warning about what is about to happen. Of course most people take the opportunity to come on deck to assist/protect their topsides. Only a few weeks ago I hailed a boat to ask if it was OK to come alongside and got the reply "OK, but we're eating." He didn't come up, but he wasn't being rude he just wanted to enjoy his meal. But he knew what was happening and wasn't suddenly surprised to hear footsteps on his side decks.
The other side of the coin was when we tied up alongside an unoccupied boat last year. We tied up and went for a meal. On our return we found a charming old man sitting in his cockpit greeting us with "I hope you got in OK. I'm so sorry I wasn't here to take your lines when you arrived." It still makes me smile. He was a real charmer.
To be honest, I think you were a little ungenerous. When you see the crew of a boat having difficulties, then your natural reaction should be to help. If this can tactfully include a little teaching then all the better.
We had the great pleasure of meeting a family in Cherbourg we knew from our home marina last weekend. When we told them we were leaving for Guernsey they decided to follow us, and we kept in close contact all the way. They wouldn't have attempted the passage through the Alderney race otherwise, but left this morning for a solo trip to Jersey after a great stay here.
I've never turned away a boat from alongside and can't think I ever would, even if I had to warn them I was leaving early.
I seem to remember the waters that I did my learning on (Essex and Suffolk rivers, 35-odd years back) being populated by assorted old fishermen and barge skippers who were absolutely brutal with anyone who behaved badly, and only slightly kinder to beginners who made honest mistakes.
I was far more scared of the local longshoremen than I was of the sea itself!
I am not sure that this was a bad thing.
We can all be kind and generous, but the sea won't be.