Should i high pass audio for real time frequency detection?
Yes, it is. If you pickup signals with a microphone you will often see enormous amounts of low frequency signals (air condition, HVAC, traffic, wind, etc.). Even in quiet rooms there tends to be a lot of very low frequency noise. 

This noise can dominate the time domain waveform and reducing it can often make your pitch detector more reliable and/or allows for a cheaper or more efficient algorithm.