There is absolutely no way I would disable protection in order to install a program, certainly not on the say so of the program maker.
I would have to ask, is the program executable digitally signed as that goes a long way towards trusting a program.
Can you attach a screenshot of the Avast Alert window with the details option selected (see attached screenshot on how).
If it is in the Quarantine, you can submit it to Avast for analysis.
