Maybe a CEO "should" because it's good for them and their company, but a healthy market regulator "should not" allow those type of transactions, in general, for the good of market participants.
I agree about your being specific about these types of transactions. At this scale, these things should be blocked.
In healthier marketplaces, acquisitions can also improve the overall health of the marketplace by improving efficiency, output, etc., while maintaining competition.
The interesting question to me in these discussions is, are there systemic changes we can make that would prevent these marketplace distortions from being possible in the first place, and what would be the negative tradeoffs? And are they politically feasible?