Company can't discriminate union members but OKAY if justified by apprehension, fear of sabotage

To consider discrimination by reason of union membership as an act of unfair labor practice, the same must have been committed to encourage or discourage such membership in the union. Here, this cannot be said of the act of the company complained of. As clearly established by evidence, the refusal to allow the employees to work and the requirement that they should stay out of the premises in the meantime while the strike was still going on in the factory was borne out of the company’s justified apprehension and fear that sabotage might be committed in the warehouse where the products, machinery and spare parts were stored. It has never been shown that the act of the company was intended to induce the employees to renounce their union membership or as a deterrent for non-members to affiliate therewith, nor as a retaliatory measure for the activities of the union or in the furtherance of the cause of the union. (G.R. No. L-19767)