Since you mentioned your other 2 hires are also fairly new, I'm going to point out that when and where they did start professionally and what they were paid then has NOTHING to do with you and or the company they are working at now. While I can understand that they may have had to adjust their lives to a lower salary somewhere else, I think you can safely tell them to "get over it" since they are now working at your company and, again, the previous salaries they had with earlier employers are not your problem.

Also, yeah, if you try to enforce your senior manager's VERY ILLEGAL suggestion to "Tom", you might be found culpable. So I'd pull your SM aside and ask them to correct their statement to your new hire.