I can't force you to discuss it further, but I am rather curious about whether you would have the same opinion if the positions were reversed. Suppose she had been born in Bangladesh, had no connection to the UK but qualified for UK citizenship by descent, and had travelled from Bangladesh to join ISIS. Bangladesh then revoked her citizenship on the grounds that she qualified for UK citizenship, although she never lived here and the UK is not in a good position to give her a fair trial, not knowing the circumstances under which she was radicalized.
Presumably you would support Bangladesh's legal right to do this, and also insist that the UK must issue her with a passport and allow her entry. But on what grounds is the decision by Bangladesh a morally correct one? It's simply a race to be the first to revoke citizenship, and it benefits the country where somebody actually resided because the other country is not in a good position to know that somebody qualifies for citizenship until they apply. The moral decision IMO is that the country where somebody was radicalized or otherwise groomed takes responsibility for the issue.
Aside from that, the law should be such that this type of situation cannot occur.
I'm going to start by saying that, in a nutshell, you appear to be calling me a hypocrite. Now, I don't know whether that was your intention, but that's certainly how it reads, and that's actually quite offensive. That may not be what you meant, though.
In either case, the short answer, then, is 'no, I'm not a hypocrite.'
To go into more detail, if I think that something is moral for me to do, then it is also moral for you to do it. If it is morally right for my country to do something I support, then the flipside of that is that it is also OK for another country to do the same thing. That's how morality works: it should apply universally, or one is displaying double standards.
I believe that every country has the right to protect itself. In the case of terrorists with dual nationality, both countries are entitled to take whatever legal steps they can to ensure, as far as possible, the safety and security of their citizens. One of the countries has to take responsibility for that criminal. I would rather it was the other one, but, if it's us, then fair enough, we'll deal with them. If the option exists to have the other country do it, then I see no reason not to take that choice- and, yes, it is a race to see who gets there first. If the individual involved is a dual national, then there's no other choice: that's a consequence of dual nationality. One or other of those countries will end up having to try, jail, or, in Bangladesh's case, shoot at the airport, that person.
Turning to your other points, I do have a few quibbles.
Firstly, you lay the responsibility for radicalisation squarely on the shoulders of the country they are residing in. That is, IMHO, slightly simplistic. Talking specifically of Begum, the videos she watched that radicalised her did not originate in the UK. What makes them the UK's responsibility, then? It is also entirely plausible that her Bangladeshi Muslim heritage made her more susceptible to ISIS' message. I'm not saying it did, just that it is a possible factor. I don't think it's cut-and-dried that Britain is solely responsible. (As a side note, the efforts by the police etc. to monitor and prevent radicalisation were pitiful. Much more could have been done to preempt the flight of the three girls to Syria.)
I also don't accept your claim that a dual-nationality Bangladeshi terrorist could not get a fair trial in Britain. I don't see that the circumstances of radicalisation cannot be fully and fairly examined- especially as that radicalisation came from online content accessible anywhere in the world. Nor is that the only part of the story that would need to come before a court. What she did in Syria, and her clear lack of remorse subsequent to her capture, are also relevant. Both these factors could be included in a trial in either country, as they are about what happened in Syria, not what happened in either the UK or Bangladesh.
Finally, I don't think a government can be forced to issue a passport. There is a human right to be allowed to enter a country of which you are a citizen, but my understanding is that issuance of passports is discretionary, and that people can be prevented from travelling.
