I've taken the time to read all the threads before posting and to think carefully about what I want to articulate.
This is obviously a very important and emotive topic and I'll do my best to put my views across with that in mind.
Also there's a lot of information to process over 4 threads and I'll apologise in advance and state that I'm happy to be corrected if I've misinterpreted anyone's comments.
Right, that said there's a lot to unpick here so I'll look to break my thoughts down according.
So I'm going to jump right in with the titles of the threads.
If you title a thread asking AIBU about white people not being subject to racism it's not surprising that posters will argue the merits or otherwise of that specific question and that doing so is not in fact, "whataboutary". It's discussing the premise of the thread in good faith.
Which brings me to my second point which is trying to understand what these threads are really about. If they are not meant to be a discussion centring a white experience, but rather a BLM perspective then what is the core of the message here?
My understanding of the OP's rationale is that white people cannot be subject to racism because they have the opportunity should they wish, to "opt out" from the prejudice they experience by choosing to "camouflage" their ethnic/religious identity by means such as changing names/accents/clothing/behaviour; something that a person who is the object of racism due to being black cannot do and as such the word racism should not be so broadly utilised.
In which case the topic at hand is not can white people experience racism but rather is the term racism itself to broad and should it be re-defined.
This I think is an interesting discussion and had the thread titles been focused on this I think a very different set of responses would have resulted.
That said I don't agree that all white ethnicities/religious actually do have the option to "opt out" of their oppression nor indeed should they have to.
As previous posters have explained there are physical characteristics that some of these people share that identify their background and are directly responsible for the prejudice and bigotry they encounter - irrespective of their name/accent/clothing. I myself have been in the company of non-orthodox Jewish colleges and seen them subject to anti-semitism by strangers simply because they are told they look Jewish (I mention non-orthodox specifically to demonstrate they were not wearing clothing that would outwardly indicate their religion).
It's also a fairly obvious point to make that if it was an option to camouflage your ethnic and religious origins so readily, then 6 million Jews and half the estimated Romany population of Europe would not have been sent to the gas chambers nor would Albanians in Kosovo been subject to genocide in the 90's.
One of the most important steps in tackling racism is to acknowledge it exists and that is again why the title of these threads is problematic, in the context of what many people describe as racism and what as a word it encapsulates.
If you say Travellers, Albanians and the Jewish community are not and cannot be subject to racism because you choose to re-define the word to only relate to skin colour the there's an argument to say you're actively disenfranchising their experiences something that's obviously upsetting and provocative.
On the other hand if your centring a discussion around the definition and application of the term racism a very different discussion ensues.
We have specific words to describe prejudice against the Muslim and Jewish communities, but not by way of example for Travellers, nor could you argue that experienced by BAME communities in that the latter falls under the term racism which is used as a "catch all" term for all acts of bigotry and prejudice.
So I do think there is merit in the OP's position that the term itself should be limited to specifically describe prejudice based on skin colour.
As an example why, if a Black Muslim is the subject of racism is that because he was black or because he was Muslim? If he was the subject of islamophobia it would be clear. It's also possible he was the subject of racism because he was both black and a Muslim, something that would not be true of a white Muslim who was described as being a subject of racist behaviour.
The issue a hand being that the use of the term racism when used as a "catch all" doesn't articulate the "double whammy" experience that black Muslim experienced in this scenario.
Equally it's also possible to argue that retaining the "catch all" nature of the word racism for all forms of prejudice is a option but there should be specific terminology used in common parlance to denote that which is derived from skin colour or a specific ethnicity such as Travellers.
In summary I do think these threads have raised some very important points and there have been many illuminating posts pertaining to the BLM movement and specificity what white people need to do to raise their game in tackling black oppression and both systematic and casual racism.
That said I think they could have been more productive if the premise of the discussion had been better articulated by the title.