Its a matter of choice.
Normally, you would want to bias your BJTs/MOSFETs to have VO1 = VO2 = 0VDC.
So if you beforehand set VIN1=VIN2=0VDC, and still want to get VO1=VO2=0VDC, you will need to set:
1. RC in order to have VO1=VO2=0V.
RC = VCC / IC; (IC = IBIAS/2 since the BJTs are matched).
2. VBE in order to have the required VBE that corresponds to IB=IC/beta = IBIAS/(2*beta).
As said, you can set VB=0VDC beforehand, and set VE to the right value, according to the IB(VBE) exponential equation.
Normally, once you set IC, and VB=0Vdc, the current source IBIAS will automatically set its voltage (VE) to the required portion to give IB=IC/beta, that is if its output voltage swing is flexible enough.
By the way, i've also started learning about differential amplifiers as part of the course Linear Electronic Circuits (Also called Analog Circuits), which deals with single-stage, multi-stage, differential and feedback amplifers.