Is it permissible for Muslim scholars to ignore Sunnah Mutawaterah and a verse in the Quran for the excuse of (Saad Al Zarae) to make what is allowed not allowed?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

The texts of revelation whether the Quran or the Sunnah of the Prophet are confirmed evidences that no one can deny with matters of Ijtihaad (a juristic opinion on matters which are not specified in the Quran or the Sunnah) on which the scholars differed in opinion, like preventive measures in avoiding things that could lead to something forbidden taking place. So, the texts of revelation have to be taken into account.

It should be noted that even the scholars who are taking these preventive measures have restricted them because that leads to hardship. So, not all what they fear could lead to something forbidden, is forbidden in their view. They provide the example of something that is not forbidden but could lead to something forbidden, for instance they do not forbid sowing grapes despite the fact that grapes could be used in producing intoxicants. The other example that could be mentioned in this instance is the dwelling of a man in a house near the one where women live.

For more details, please refer to Fiqh books. 

Allaah Knows best.