Hey
If you draw the small signal diagram of the BJT (T-model), then the emitter resister Re is in series with the small-signal emitter resistor. This means that when an input voltage is applied to the base of the transistor it is divided between the two resistanses. This will of cause lower the signal across the small-signal emitter resistance. It is only the voltage across this that is amplified. In this way you can apply larger signals to the BJT and still consider it linear.
The price is of cause gain.