Zinc blocks DHT, which is the hormone which promotes all other secondary sex changes in the body including deepening of the voice, aggression, libido, facial hair and physical); (testosterone is only responsible for muscle mass growth - DHT is responsible for all other "masculine" characteristics) by increasing your zinc dosage to above average levels your are blocking DHT to a greater amount; this results in a very passive state in the zinc user in question in which they may feel good, but act in a very passive way.
Notice what happens when you remove excess zinc from your diet and stay at a normal intake (10-20mg per day); you will feel much more aggressive and will start to exhibit feel DHT at work and its side effect (such as afore mentioned strength gains and aggression).
Ever wondered why people who supplement zinc report a clearing up of acne and oily hair almost simultaneously? You guessed it, zinc blocks DHT and therefore the androgens responsible for the acne. Same reason zinc supplements are given to aggressive autistic and adhd children - to calm them down.
In brief, excess zinc will make a person quite passive and non-aggressiveness due to the afore mentioned lowering of DHT levels. (It does have other benefits such as clearing up acne etc. though/calming aggressive behavior) - you be the judge.
Zinc is an essential element - I make sure to get between 15-20mg a day from food sources. Just don't overdo it; it can tun you into a bit of a bitch.