Concluding that "when the entire record is considered there was substantial evidence to support the Board's finding that [employee's] discharge was the result of his having presented a grievance to the management" even though employee was overheard referring to company's superintendent as "the horse's ass" and was thereafter summarily discharged
Noting that the test for violations of sec. 8, now codified as sec. 8, of the NLRA is whether "the employer engaged in conduct which, it may reasonably be said, tends to interfere with the free exercise of employee rights under the Act," and that actual or successful coercion need not be shown in order for the Board to find a violation