For effective deterrence I think there has to be an expectation that the response to a tactical nuke is the big red button.
(the link I sent is a bit meandering but seems to indicate Russia has ~20x the tactical nukes that NATO has deployable in Europe, although of course categorization always muddies waters. That would seem to indicate West indeed does not consider a tactical nuke to be the appropriate response to another tactical nuke).
The impression I have thus far is that this is because
a) Russia has not invaded/declared war on "the West" in a meaningful way yet: it has invaded the Ukraine, which is not a member of NATO, the EU, or any other specific mutual defense pact with the rest of "the West".
b) Relevantly to this thread, Russia has not yet used any forms of warfare that truly cross the line into "mad dog that needs to be put down at all costs". The cluster bombs are pretty bad, yes, and reflect very badly on Russia, but they're still conventional munitions.
If Russia breaks out chemical, biological, or nuclear weapons, the calculation on (b) changes. Doesn't automatically mean everyone's going to jump on them—I don't pretend to know how any given country would respond to that, even my own (the US). But it at least means they have to start rethinking whether (a) remains relevant to their decision not to get directly involved.