I disagree about it being logical to replace it. There's no real good reason not to keep it if we think it's still useful. I feel it's contentious because that's a lot of money to spend destroying stuff that could still provide benefit for many years to come.
Of course, to actually discuss this, we need to answer the real question of whether we even want to keep the ISS...
If we agree something like this is useful to have in the long run, if we destroy the old one, we have to get every party involved (or a new group of countries) to agree that this is worth spending the money on building an entirely new ISS. My gut feeling says that won't happen in the current geo-political climate. If we destroy the ISS, that's the end of the road.
We could, of course, all agree that it's too expensive maintaining the ISS and we should just abandon any such future projects. While this might well be popular with some governments trying to save money, we will miss out on all that research and international collaboration. Honestly, I don't know what value that research is nowadays, but I assume there must have been some or we wouldn't have done it originally and manage to convince lots of countries to participate in spite of their ongoing tensions.
Or the third option - continue to build, using the existing ISS as a base. We could send up small modules piecemeal and bolt them onto the ISS. It's not like the ISS even has to end up as the centre, it could end up entirely on one side and at the point it's really no longer useful for operations, it would still have value as a storage space, the parts could be ransacked for repairs, it would even provide some impact protection from random space junk.
Other than potentially making the "new" ISS a bit less maneuverable, or random bits falling off and hitting the new structure (not sure if that really happens or only in movies), I don't really see any downsides to keeping the old ISS attached to any new structure. And keeping it safeguards us against completely abandoning future co-operative research.
I guess one perceived downside might be that the US wants to go it alone with some secret projects, and doesn't want to build anything attached to the ISS to reduce the possibility of a hostile takeover.