There are regular surveys that cover how many people are in unions and the overall perception of unions. The numbers back up the idea that unions are dying and people don't think highly of them.
Membership is definitely tanking.[2]
[1] https://news.gallup.com/poll/12751/labor-unions.aspx
[2] https://www.bls.gov/opub/ted/2019/union-membership-rate-10-p...
~40% want to see grow to ~30%, giving them ~57% share of people with an opinion.
The confidence stat is silly - I don't have a huge amount of confidence in unions either because of their obvious decline in the last few decades.
Don't really see how you can see the [1] poll and not think that there is clearly a fair bit of support for unions. [2] seems completely irrelevant to popular opinion, which is what we were discussing.