Was Benjamin Harrison a bad president?

The answer to this question really depends on what you mean by the word "bad." A bad president could be one that is merely ineffective but not detrimental to the nation, a president who is detrimental to the nation (either intentionally or accidentally), or a president who is highly effective but is focused on policies you personally disagree with.
Benjamin Harrison appears to have been a president with both personal and official integrity. He maintained a reputation for integrity despite close examination by political opponents. Harrison helped implement new tariffs that increased federal revenues but were unpopular with the general public. He also helped implement the Sherman Anti-Trust Act, which outlawed monopolistic business practices and supported voting rights for African Americans.
By all accounts, Harrison seems to have been an ordinary president. He accomplished some good things and some unpopular things, but he does not seem to have harmed the nation through his actions.