Is there something wrong with hiring engineers from a competitor? Should they have had a no-poaching agreement like Apple and Google had a few years ago? That was deemed illegal if I remember correctly.
In and of itself no, but courts have ruled that there's a distinction between hiring people to make use of their talent vs. hiring people to deny said talent to the competition.
Was Microsoft targeting Borland employees because Microsoft was looking to make use of their talent for their own products; that's legitimate. However, if Microsoft was hiring Borland employees for the purpose of keeping those employees from working at Borland; that's potentially predatory and violates antitrust laws.
Note that it's not even in the employee's best interest in the case of predatory hiring. Much like with predatory pricing, once Borland goes out of business as a result of said practice, Microsoft is unlikely to continue retaining many of those employees or paying lucrative salaries and the overall pool of talent as well as salaries is likely to shrink in the long run.
It's the nature of predatory actions that they hurt the actor in the short run but benefit them in the long run whereas the public gains in the short run but is damaged in the long run.
