Tyler tries to cure my immigration backlash confusion, but not to my satisfaction.  The overarching flaw: He equivocates between two different versions of “backlash to immigration.” 

Version 1: Letting in more immigrants leads to more resistance to immigration.

Version 2: Letting in more immigrants leads to so much resistance to immigration that the total stock of immigration ultimately ends ups lower than it would have been.

Backlash in the first sense is common, but no reason for immigration advocates to moderate.  Backlash in the second sense is a solid reason for immigration advocates to moderate, but Tyler provides little evidence that backlash in this sense is a real phenomenon.  I say he’s engaged in journalistic hyperbole.  If you seek clarity rather than attention, it’s far better to consistently stick to Version 2 for “backlash,” and call Version 1 mere “resistance.”  That’s what I’m doing from here on.

Point-by-point:

1. Had the UK had much freer immigration, London would be much
more crowded. 

In the very short-run, of course.  Before long, however, firms build more housing.  Outskirts become more like central London – what’s so terrible about that?

With truly open borders, people would be sleeping on the
sidewalks in large numbers.  London itself would have turned against
such a high level of immigration, which quickly would have turned into a
perceived occupation.

Probably true in the short- and medium-run.  But it’s still far from clear this would lead to genuine backlash as defined above.  In any case, there’s no sign existing immigration has had any such effect, even in London.

2. Changes often have different effects than levels:
“Where foreign-born populations increased by more than 200% between
2001 and 2014, a Leave vote followed in 94% of cases. The proportion of
migrants may be relatively low in Leave strongholds such as Boston,
Lincolnshire, but it has soared in a short period of time. High numbers
of migrants don’t bother Britons; high rates of change do.”

In other words, had there been higher levels of immigration into
non-London parts of the UK, the backlash may well have been stronger
yet.  For a careful reader of the Caplanian corpus, that is in fact a
Caplanian point and I am surprised it did not occur to Bryan.

I’d really like to see a multiple regression, because there’s very likely a strong negative correlation between immigration levels and immigration changes.  In any case, I’m surprised it does not occur to Tyler that today’s changes are tomorrow’s levels.  This is entirely consistent with my claim that high enough immigration will eventually destroy nativism.

3. The highest quality and most easily assimilating immigrants will
be attracted to London and the greater London area.  Packing Birmingham
with London-style levels of immigration won’t give you London-style
immigrants, nor will it turn Birmingham into London.

Why not try and see?  Patterns often generalize.  There’d be no social science if they didn’t.

4. London already has a population pre-selected to like immigration. 
Spreading London-like levels of immigration to the rest of England
wouldn’t make immigration as popular elsewhere as it is currently in
London, even if that immigration went as well elsewhere (which would not
be the case, see #3).

Was London “pre-selected” to like immigration before it had much immigration?  Where’s the evidence?  How could we even tell?

5. Post 1980s, England underwent a very rapid and significant change
with respect to the number of immigrants it allowed to stay in the
country.  If that wasn’t fast enough for the open borders idea to avoid a
backlash along the way, then perhaps the new saying ought to be “Only
whiplash avoids backlash.” But that won’t exactly be popular either.

I never said immigration was popular.  In fact, I’ve repeated said the opposite.  I’m also happy to admit few people would decry immigration if it barely existed.  But Tyler’s backlash thesis has to claim something much stronger to be interesting, and he presents little evidence in favor of that stronger claim.

There is a very simple interpretation of current events, including of
course the Trump movement in the United States.  It is “the backlash
effect against immigration is stronger than we used to think, and we
need to adjust our expectations accordingly.”  When Bryan writes “I know
he disagrees, but I honestly can’t figure out why”, I think he is
simply afraid to stare that rather obvious truth in the eye.  In any
case, it’s staring rather directly at him.

I agree that anti-immigration sentiment is staring me in the face, and freely concede that I am afraid of it.  But that hardly shows that relatively open immigration is self-defeating.  And if it doesn’t mean that, the language of backlash is empty.

Question for Tyler: Suppose Trump loses, taking the whole Republican Party down with him.  Unified Democratic government then further liberalizes immigration.  Would this show you were wrong to claim the U.S. had an immigration backlash in 2016?  If so, your backlash thesis is far less obvious than you claim.  If not, your backlash thesis is far less scary than you claim.