No, you cannot deactivate the Multiple Units of Measure plugin because of the following reasons:
Multiple Units of Measurement affects the entire master data and all transactions across the application.
Multiple Units of Measurement is used in sales as well as back office inventory transactions like PO, Goods Receipts, stock transfers etc.
Deactivating Multiple Units of Measurement will require the application to recalculate all the open transactions and also the inventory valuation in the application
Moreover, deactivating Multiple Units of Measurement can potentially lead to rounding off discrepancies because transaction values will have to be recalculated for the base units of all products.
To ensure data integrity and consistency deactivating Multiple Units of Measurement is not allowed