Ok here is my take on this (and it comes from experience...not a "bloke" thing.....
Your dad may very well be right in that the angel will "learn his lesson"!!
I have had fish that were very aggressive and in certain cases I would seperate them for ahile in their own tank.
When re-introduced into the main tank they were indeed less aggressive.
Now I am not saying this will be the case with your angel, but your dad is not "way off" in his thinking.
Now for my "not going to be popular comments"...................
Your opening post about your dad was very disrespectful!! While it may be true that you know more about fishkeeping then he does, and you may not like the fact that he does/did not listen to you, you came off in that post like a little spoiled knowitall!!!
If this is the way you sounded here, then perhaps this is the way you came across to your dad.
Rather than "telling" your dad the way things should be, you should have had some back up ready to prove your point!!
Being the "experienced" fishkeeper, you should have forseen the possibilty of this happening and not been so quick to stock your ten until you made sure the "family" tank was going to be conducive to the well being of your angel!!
Bottom line here is this...........you knew going into this "family" tank thing that it was just that......."a family tank"!!
You only paid for half of it and why shouldn't the others have the right to put what they want in it as well?? It sounds as if you thought this was a way for you to get a bigger tank for your angel and that the rest of the family should be subject to only picking fish that will be able to get along with your angelfish!!
Perhaps you should take the angel out and put the tetras in the family tank and put the angel back in your ten!!
Sorry I could not agree with you and the rest, but IMO you are as much to blame as the rest of the family for the tank's situation!!
CM
