Any employer that's a union buster deserves to be boycotted until they close and something better comes along to fill the need (which it will do quickly). In truth, the grocery supply chain/warehousing being so strongly coupled with the supermarkets is the primary point of inertia in the US regarding grocery stores opening where they're needed. Most independent distributors only focus on restaurant contracts, because they can achieve higher margins there.

Edit: Not that coop distribution doesn't exist. For example https://en.m.wikipedia.org/wiki/Associated_Wholesale_Grocers who are represented by the teamsters in four of their distribution centers.

If a company genuinely cares about their employees, they'd support them unionizing.