"I finally felt at home because the increased diversity of experience meant that I wasn't alone anymore"

that feeling of discomfort you felt beforehand is exactly how a native Canadian feels when he/she is around foreign immigrants. that feeling of comfort is exactly how a native Canadian feels when he/she is around an English speaking one. having experienced this, you should have empathy for the native

"I feel much more in common with other immigrants (particularly from my home country) than the White Canadian Culture"

of course you do, because you're not assimiliated. why would you feel affinity for a culture that isn't you? this is the same exact logic of the native, who feels uncomfortable with a foreign culture

"I am confused why the acceptability of immigrants should be judged on their apparent difference from the 'in group'"

I don't like the term "acceptability." everyone should be "accepted." what I'm speaking to is the reality that someone with cultural similarities/ethnic ties will have a likelier probability of assimilating and getting along with the natives than someone with no such similarities.
nations are just constructs that can easily be subverted by foreigners. foreigners pose a potential danger (including English speaking foreigners). and someone with cultural similarities/ethnic ties is a known commodity, and is thus less of a danger.
of course, foreigners can also potentially provide enrichment and new viewpoints, which is why it's dumb to discount them entirely. and like I said, strangers should always be treated respectfully. but they should be dealt with with caution.

"Who is the 'in group'?"

well the "in-group" depends on where you are. in greater Canada, the in-group would be native Canadians (i'm not describing First

"Nation...I mean people who were born and have lived in Canada for generations). in the tech world it tends to be immigrants."

"What are the customs? Who gets to decide them?
the nation has a culture spanning several centuries."

do I get to define the 'in group' or do I have to wait a few generations?
if you assimilate then you can be part of the in-group. otherwise you are "just an outsider
Why should they 'learn the customs' at all?"

why would you move to Canada if you don't want to be a part of the culture, unless it's to be a parasite on the nation that Canadians have constructed

"racism lite disguised as something to do with "risk assessment"

whether it's racist or not really has to do with the actions of the in-group person. someone can be racist and use my spiel as an excuse. another person can be not racist, but want to spend time with people who share customs/culture

"I'm not denying my privilege"

when you spend time in immigrant-rich environments, you feel more comfortable because you're around others like you. I would feel less comfortable around them. the fellow immigrants would get along better with you. does that mean you have some "immigrant privilege" that I wouldn't have? no, because that's a dumb concept.
you're better

I never said "better." I said more assimilable