Búyào dǎ zhe zhèngyì de qíhào zuò bù zhèngdāng de shì.
Don't use justice as a pretext to do improper things.
Tips
usage
旗号 most often appears in the pattern 打着...的旗号 (under the banner of / using ... as a pretext), usually with a negative connotation - someone claiming a noble reason while doing something else.
