While its true that methane is a much stronger greenhouse gas then CO2, it also breaks down in our atmosphere within 20 years so there is no accumulative effect.

The CO2 you emit during your groceries shopping trip in contrast stays in the carbon cycle for hundreds or even thousands of years, contributing to climate change that whole time.

Also, many people drive a lot more then 8 miles every 2 weeks. And if you're just driving 8 miles every 2 weeks anyway just keep your old gas car. This isn't a outright ban.

The bottom line however is that we need to do all the things. complaining one measure doesn't fix everything is a BS distraction.