First, Mars candy is not made by union workers. Second, the billionaire family that owns the Mars candy company has been leading the fight to repeal the Estate Tax, and so is a threat to democracy.
Fortunately, there are many candies that are made by unionized workers.
This here link gives a list of candies that are made by union workers.
There are lots of good candies here! So, there's no need to buy non-union candies.
As for Mars and the Estate Tax: the Mars family has a number of billionaires and has been leading the lobbying effort to repeal the Estate Tax. See, for example, this Wikipedia article
Many members of the Mars family think that they should be handed billions of dollars without having to work for it.
Kind of like welfare, except they don't call it that.
Not only that, but they think they should get this money without even paying tax on it.
Of course, the rest of us both have to work for the money we earn, and we have to pay tax on it.
Allowing the super-wealthy to pass along billions of dollars to their heirs, tax free, would set up a permanent aristocracy of inherited wealth and power. Didn't we have a revolution against that back in 1776?