Straightforward is fairly neutral. Frank means being honest and direct, even though - as in your sentence - it can occasionally be hurtful. Outspoken carries more of a negative connotation and often implies expressing views or opininions that you know are unpopular.

Is Outspoken positive?

outspoken: This is usually a positive attribute. An outspoken person may speak out in defense of the voiceless or the oppressed and against evil. Such a person may also be a devil's advocate or a rabble-rouser.

What does it mean if someone is outspoken?

1 : direct and open in speech or expression : frank outspoken in his criticism — Current Biography. 2 : spoken or expressed without reserve his outspoken advocacy of gun control.