I suppose I may have read more into what you wrote... I'll try again:
I'm assuming that you want to suppose we take the stance that Christianity is man made.... what do we do with that revelation?
I simply left.
At first, I tried to reconcile christianity. I tried excusing all of the 'dung' (if you will). That didn't work, for reasons I pointed out in the almost debated paganism topic in the MJ section. There, I pointed out, at least according to the Tenach:
1) Ignorance is not an excuse. At first I tried expressing that most christians were merely ignorant, but this crumbled when looking at II Sam. 6.
2) G-d explicitly states we are not to worship Him in the same way the pagans worship their deities. You see, at first, I tried to dispell the pagan influences by stating 'christians are actually worshipping G-d'. However, it became evident that G-d demanded we worship Him in the manner in which He prescribed, and not in the same manner as that of the pagans.
So, with my own 'excuses' pushed to the way side, I was left unable to reconcile christianity. This led me to attempt to "toss out the dung" while maintaining what I felt was right and good.
I soon found out I was tossing out the entire thing... the overwhelming majority of it was dung.
I then attempted to rebuild my beliefs upon the "new testament" and the "messiah". This too failed. You see, the Messiah continously pointed to the Torah and the Father, never to himself. Sure, he was a beacon of light that led me to an end, but was not the end in itself. I also realized the dangers of building
any doctrine soley on the "nt". (I will explain more of this later)
I have finally resolved to pitching aside the last 2,000 years and starting from scratch. The apostles instructed the early messianics to go to synagogue. Never did they have their own "church" or congregation even. Here is clear instruction. Start with the basic Noachide covenant that was given to all mankind. Then, go to synagogue on Sabbath and hear the torah (moses). There you will grow in the rest of righteousness.
Never was there to be a seperate religion called "christianity". Even following the most basic principles in the Brit Chadasha (nt) you will be led to Judaism and the synagogue. Anything else is simply put... man made.
I evolved in my view over time. First, I attempted to reconcile christianity, then to 'clean it up', and finally tossed it out. Then I went from attempting to build my faith upon NT principles, to finally where I am today... totally Judaic in mindset.
I'm not denouncing the value of that which is tainted, but it is simply that... tainted... man made. The Judaic mindset, as you pointed out in your OP, is G-d ordained.

I simply feel you went one step too far in declaring the other island was made by G-d as well. We merely diverge on that one aspect achi.
Shalom,
yafet