Orrrr we could do more than one thing at once?
In any case, a "sudden, full-blown glacial period" has never happened according to any geological record we have. The most "sudden" have happened over centuries. The actual, demonstrated suddenness of current warming trends is a major part of the problem.
There are a bunch of problems in your post (I have no idea where you get the idea that we're in a glacial period, these are just labels, but no one calls the Holocene anything but an interglacial; it is well established that Milankovitch cycles do not explain current trends; current atmospheric carbon will be there for centuries to come and will not stop warming us even if we were to stop all emissions today; you neglect ocean acidification, sea level rise, etc), but the fact remains that its ridiculous to assert that "we should have our eyes" on one threat instead of another, when we could have much more scientists and funding for asteroid detection if someone would exert some political will. That is what's necessary, not trying to minimize other threats with specious (at best) arguments.