Are they being unreasonable?

I played my second 1850 game a few nights ago at my LGS and I won't go too much into the battle but I did win but only because one of the players watching was helping me and my opponent (he was showing us some of the advanced tactics and my opponent was curious too so he encouraged it).  I don't really consider this a win because I didn't do it myself.

None of this really is the point of this post (although I will be posting more about my thoughts of the game and my list itself).  The reason is the conversation I had with two fellow players after the game.  I was discussing my desires of my list and its theme (an Armored Company from the Blood Ravens) which they didn't seem to have any real issue with until I told them one of my ideas was to make a 1st Company of Blood Ravens using the Grey Knight Codex.

To be fair this didn't cause a immediate 'Nerd Rage' it was more of a slow burn as I listened to their opinions and such about how some might feel that I was power-dexing then when I explained to them that Grey Knights were the best codex to to represent what I feel a veteran company (1st company) of Blood Ravens would be.  They both insisted that I could not do this and that it would violate the lore of the codex.

Now let me state that I had no intention of cutting any corners I was going to be buying the Grey Knight models, shave off the Inquisitorial icons, buy some custom shoulder pads and paint them up in Blood Raven glory!  So my red Grey Knights were apparently unacceptable because it would smack in the face of those who love the lore.  I'm not stating that I'm playing a successor chapter of Grey Knights or insisting that the Blood Ravens are...but simply that I'm using what I feel is a codex of Veterans as a 1st company.

Here are some facts about the Blood Ravens:

They do not know who their Primarch is
>This means they could belong to any chapter, even chapter 666.
Work closely with the Inquisition
>This would explain why the Inquisition is in the codex
They have been gifted Inquisitorial Weapons and Armor in the past
>Psycannons?  Gabriel has a Nemesis Daemon Hammer, and one of the Librarians Nemesis Force Sword.
They have not been mind-wiped by the Inquisition unlike most other chapters
>This means they know of the Inquisition greatly.
The Grey Knights have come to assist the Blood Ravens many times
>This gives me ideas like making Paladin squads that are still Grey Knights to 'assist'.

A vast majority of the Blood Ravens are at least latent Psykers
Blood Ravens have been known to have moments of 'clarity' during important battles where their speed and strength go beyond that of even a Marine.

Here is why they are saying I can't do this:

Only GW is cannon, all other sources (including Black Library & Forgeworld) are not.
>Even though both those mentioned companies are owned and endorsed by GW?
Grey Knights have access to gear that no other forces do
>You mean like Nemesis weaponry that Gabriel has?
Grey Knights aren't Space Marines!
>Oh?  Well the first few paragraphs in the codex say otherwise.
You can't use Blood Ravens because they are documented in the Space Marine Codex
>So?  This was before the announcement of the Grey Knight Codex.

Now to continue my thought with the previous reason.  They are perfectly okay with me making up a chapter to use as Grey Knights, it is the fact that I'm using a previously known chapter as space marines.  So basically they wouldn't want me to use blue models with gold lining on them and call them Ultramarines but it would be okay if I took blue models with gold lining and called the 'papa smurfs'.  No I'm not joking they said that would be okay.

So?  Thoughts?  I've decided that that I'm going to do what I want because I'm not gaming the rules and playing the game the way I want to.  Literally their only problem is that my Grey Knights would be red and called Blood Ravens.  I wouldn't be proxying but converting...and since 'this has never happened' I shouldn't do it.

Let me know..."Knowledge is Power"