I don't really think this is that bad. How'd "they go low, we go high" work in 2016? I'd have more of an issue if this was said toward another Republican like Cruz or Rubio, but Trump is different.
Going low against Trump doesn't work either.
Remember Rubio and his "little hands, you know what they say" and a lot of other flame-baiting he did of Trump?
Absolutely, and that's a good point. It doesn't work for most people, but I think Biden is different. I just don't think Biden would let himself get knocked around by Trump like Rubio and others were in the primary debates.