First, Glassdoor indicates Lochmead employs fewer than 50 people in JC, and Indeed agrees. Not exactly "big". Guaranty is cited in the 1000-5000 range; probably on the low end of that, given that it's JC, but regardless, it's two orders of magnitude higher than Lochmead. Hell, the Shadow Hills Country Club is bigger (51-200). 5 seconds of research would have been wise here.
Second, it doesn't matter how big a company is; if it's not their sign and not on their property, they have no control over it. Being a big company wouldn't give them the right to go onto somebody else's property and take the sign down. What is it you're wanting them to do exactly about the Trump signage? Give JC an ultimatum of "All citizens must comply with our company political views or we leave"? Even if that weren't abhorrent (and frankly more of a Trumpist-style tactic than of the left), it wouldn't be practical for a dairy. Lochmead can't relocate their cows to downtown Eugene.
The stuff about the masks, yes, they should do a hell of a lot better. But that is not the topic at hand. The topic is the "Trump Country" signage, which nobody has suggested is connected with Lochmead in any way. You're lashing out at this company with no evidence whatsoever that they have anything to do with the complaint here.