How do you think it would go if I treated my girlfriend like a man?
How are you going to treat her like a man?
I am going to be brutal about life no matter her feelings.
Your gf might have sensitive feelings and you treating her brutally would be inconsiderate and harmful. Avoid hostility by treating her with dignity and showing respect for her feelings.
I think I prefer caressing her feelings and then punching her in the gut with the truth.
That sounds very aggressive and abusive. That kind of approach in a relationship will certainly cause long term resentment problems. If you can't show her the respect she deserves, then you need to let her find someone else who can.