Beef is not to blame for this, though. Beef just happens to be the most economical right now. If it wasn't beef, it would be something else. Possibly soybeans since they are the world's largest exporter of them.
Human consumption of soybeans requires less farmland than human consumption of beef, because humans can eat the plants the cows would've needed to eat.
So less rainforest needs to be felled for the same amount of nutrition.
Arguing what the land should be used for is the point. Some uses are more destructive than others.
"If we didn't put gasoline in our vehicles, we'd just put something else in them, so arguing over what to put in our vehicles for fuel is besides the point."
Whether they grow soybeans or beef or doing whatever they are cutting the same amount of trees. The crop choice doesn't change the fact that forests aren't protected, and the market will expand to fill available space like a gas.
The Amazon rainforest is being destroyed to grow more money. Money is fungible, if beef were banned they's cut the forest to do something else with the land.
If it's being cut down for beef it _might_ be cut for something else. You can only control what you can control. Maybe ecotourism would be more lucrative if beef were off the market.