What do you mean bad for dancing? If you mean a person can lose flexibility and plasticity? It is partly true I have not seen any bodybuilders who dance gracefully.
1) Perhaps an inflexible chest cannot be extended the way dancers need it to be. (Thus leading to suboptimal posture).
2) Perhaps a heavy chest may pull the back & shoulders inwards. (hence - bad posture).
3) Perhaps a heavy chest taxes the upper-back muscles too much. (therefore - waste of energy, in order to keep proper posture).
4) Maybe it's just "bad" aesthetics. (like how I once heard that developed Trapezius aren't something one would like to see in dance).
There are two main types of training; sometimes they overlap each other. The first one targets strength and second one functionality.
Would you please define 'functionality'?
Is strength not functional?
Here is an example of great functional training that is good for strength and for functionality, that dancers can u
The second one has some nice exercises. (Sadly, not for the chest).
But I have lost some flexibility, in the recent months, and you helped me decide to want to start doing Yoga.