Trump (and Clinton) had record-breaking unfavorable ratings during the campaign. Your point about "less-bad" carries a lot of weight, in my opinion (and would have been the case regardless of who won the election). And step back and think of it: half think bad, half think good. Is that a situation you'd like to consider "not bad" in the grand scheme of things? Mediocre sounds like a fairer assessment, on average. And frankly I think we'd all prefer a solid "good" rather than an ambiguous "not bad".

Doesn't make him not a bad guy.

Less than one-quarter of the country, actually. Half the country didn't vote.