I have so many strong disagreements.
First, GP is nowhere near "half-right". Most egregious is calculating a CFR which is one fifth of the true value (as best we know with the current data). This is much closer to "absolutely wrong" than "verifiably correct", so no, "half-right" is absolutely a stretch in my book. In terms of absolute severity COVID is roughly 10 times deadlier than the flu, so there is no comparison here. And this is before we even begin to talk about the lasting effects of the disease. Suffice to say that there is no argument in terms of severity; COVID is much, much worse than the flu.
Second, comparing four months at the beginning of the pandemic when the disease was early in its spread vs. four months of endemic flu season (where the flu virus already has a sufficient foothold across a wide swath of the population) is completely erroneous. A much better comparison (though still imperfect) would be to measure across the same time period (December-March) with the same societal mitigations. In the last month, we've seen nearly 80,000 COVID fatalities in the US, so if we want to assume a similar rate over the next 3 months (likely an underestimate given the current upward trend), that's 320,000 deaths. And that's with fairly substantial behavioral restrictions to reduce the spread of the virus. You also neglected to mention that the 2017-2018 flu season was the worst in the last 10 years, where most flu seasons attribute around 40,000 deaths in the U.S. each year. So, even if we decide to ignore the fact that COVID cases are already suppressed due to behavioral mitigations, and me being generous with all of these estimates, at the very least it is four times worse than the worst flu season we've seen in the last 10 years. In reality, COVID unabetted is probably on the order of 10 flu seasons wrapped into one.
Come March we'll have a better estimate of flu deaths for this season, but I wouldn't be surprised if the restrictions see the number of flu fatalities drop below 20k or even 10k. Granting some intellectual honesty, the stats would unfortunately be significantly confounded due to COVID-induced strain on our healthcare system, and the fact that many individuals who would have died from the flu are now dead from COVID instead. But as a loose comparison, I foresee that ~20 times more people will die from COVID this winter than from the flu.
Like you said, policy is a different matter. Obviously it's worth discussing varying isolation strategies so that low-risk populations aren't significantly affected by the lockdown measures, while high-risk groups are isolated and supported. But that is a completely separate discussion. My main concern is with speech that abuses numbers and proliferates a societally-harmful mentality without discussing any of the actual nuances and trade-offs of the issue. As a suggestion for future commenters, if you want to try to compare the harm of lockdown measures versus the harm of the disease, you better make sure that your numbers are accurate before moving on to cost-benefit analysis.