AR, There are other things to consider I was just giving an example. Christ said you will know them by their fruits and he was speaking about going out and sowing the word so God would reap a harvest. Mr Phelps shows no fruit, nada, nothing!
14"Again, it will be like a man going on a journey, who called his servants and entrusted his property to them. 15To one he gave five talents[a] of money, to another two talents, and to another one talent, each according to his ability. Then he went on his journey. 16The man who had received the five talents went at once and put his money to work and gained five more. 17So also, the one with the two talents gained two more. 18But the man who had received the one talent went off, dug a hole in the ground and hid his master's money.
19"After a long time the master of those servants returned and settled accounts with them. 20The man who had received the five talents brought the other five. 'Master,' he said, 'you entrusted me with five talents. See, I have gained five more.'
21"His master replied, 'Well done, good and faithful servant! You have been faithful with a few things; I will put you in charge of many things. Come and share your master's happiness!'
22"The man with the two talents also came. 'Master,' he said, 'you entrusted me with two talents; see, I have gained two more.'
23"His master replied, 'Well done, good and faithful servant! You have been faithful with a few things; I will put you in charge of many things. Come and share your master's happiness!'
24"Then the man who had received the one talent came. 'Master,' he said, 'I knew that you are a hard man, harvesting where you have not sown and gathering where you have not scattered seed. 25So I was afraid and went out and hid your talent in the ground. See, here is what belongs to you.'
26"His master replied, 'You wicked, lazy servant! So you knew that I harvest where I have not sown and gather where I have not scattered seed? 27Well then, you should have put my money on deposit with the bankers, so that when I returned I would have received it back with interest.
28" 'Take the talent from him and give it to the one who has the ten talents. 29For everyone who has will be given more, and he will have an abundance. Whoever does not have, even what he has will be taken from him. 30And throw that worthless servant outside, into the darkness, where there will be weeping and gnashing of teeth.'
It should, of course, be noted that weeping and gnashing of teeth is biblically the pastime in Hell.
That's where the No True Scotsman fallacy comes in. There are obvious criteria for being certain things. For some things the problem comes in defining the absolute core requirements of membership that nobody can disagree with. You can say he's No True Scotsman if he's from Bulgaria. It's easy with the Scotsman, where was he born? Christianity is more difficult, but I think the three requirements you mentioned are the core ones, and anything beyond that represents your particular interpretation of what it means to be Christian, thus invoking the fallacy.
Christ said you will know them by their fruits and he was speaking about going out and sowing the word so God would reap a harvest.
Mr. Phelps puts more effort into sowing the word of God as he sees it than most Christians, that's why he's famous. Personally, I think he just puts too little emphasis on the New Testament, instead emphasizing the pre-covenant angry God.