Can benzodiazepines or anti-tension drugs like valium, xanax, rivotril etc. reduce the toxicity of a person's personality ?

Not really. If taken in doses to affect a "change", it would just make them drugged. They could still be toxic but sleepy/tired.

Drugs are not changing personality traits, they may control symptoms perceived as negative or unjustified. Would only use them if so prescribed as benzos are high risk drugs due to habituation and long term well proven deleterious effects.