Do you have any source for this? It seems hard to believe but I haven't been able to find any studies yet. The best I've found so far says unionization has no impact on business survival: https://www.princeton.edu/~davidlee/wp/unionbf.pdf.
I'm also skeptical that you could really study this effectively, since non-unionized employees tend to benefit when unions are formed elsewhere in their industry. You'd need to compare a group of companies that unionized against a group of similar companies in the same time and place that didn't unionize and also were completely unaffected by the mass unionization of the first population.
Also I'm not sure what "supporting logic" is, I presented my logic and you can disagree with it if you want (usually using different logic, which you haven't presented), but there's no such thing as "supporting logic".
I don't think you understand what the price of a stock means ...
Well, the context here was your assertion that unions don’t act in the “long-term interest of a business”. Now, most people understand that share prices are bets on the future value, but also that it’s not a direct relationship because there’s an inherent tension between long-term and short-term interests. That plays out in questions about how much or whether to pay dividends (which has seen a big multigenerational shift in investor preferences), and whether a move which raises share prices is a long-term detriment.
We’ve seen a lot of the latter discussed here lately with tech companies doing broad layoffs to satisfy activist investors, despite research suggesting that companies making unforced layoffs tend to underperform over the long term.