The way I see it is you'd go to church (or whereever your place of worship may be)..... we all know its not fair taking them out of the ocean.... its less fair putting them together.... its less fair not feeding them properly.... etc. etc. ..... everyone has their own personal moral limit, where things are exceptable to them or not......
It's not fair to get a dog and not walk it - its not to say its cruel, or that you don't love the animal....... but its not 100% ideal.... but neither is it 100% ideal to lock the animal up for 8hrs a day, even if you do walk it..... you can argue it should be left out in the yard all day..... then you can argue it should on a farm......
The entire hobby is realy just a compromise - folks can argue about how rightreous they are, or are not, but the second you go into a shop and buy a fish like an angel, you are wrong, and from that point on you (we all) are perpetually trying to make it right by doing what we feel is "our best" to eleveate the guilt.......
Everyone can gauage what your "best" is..... for me its providing a home with a minimum of stress to a the point where I am not wasting my time and money.... I am comfortable knowing that I cannot really do much more for the fish I choose, and I aim to provide more than the recommended minimum..... and to be heonst I think that my fish tend to do a little bit better than average...... and I tend to recommend that others would follow this path...... why? Mainly because it lets a much larger margin for error....... it really is hard to go wrong.... but if you push the boundaries, unless you are dilligent in your care for the animals you will at some point become "unstuck" and the disaster will be recorded as a "mysterious death".
I don't believe in telling people they are worng because they disagree with me. If people are wrong and they know it, well I'm hardly going to change their minds, so there is no point in wasting time agruing - if people are wrong through ignorance, well the best solution to ignorance is education..... I try my best to judge which of these three catagories people are in - and then repsond accordingly
........... hopefulyl I've got the balance right here.
In conclusion, as previous, if you are up to the challenge, and are going into it eyes open, and realise what is needed for long term sucess and you think you arecapable of doing what is needed, then I say go for it....... even it is not not how I would "choose" to keep angelfish and it is not how I would "choose" to use a 500 gal FOWLR tank....... but I don't think your wrong doing it, so long as you do it right
Good luck - Matt