Thank you for your question. Please permit me to assist you with your concerns.
My apologies but that does not appear to be illegal. If you are formally appearing at work for only 7 hours a day rather than 8, the employer can choose to limit, modify, or cut your hours based on your schedule. That is not retaliatory, it simply shows the actual amount of time you spend working for the employer.
As for accommodations, the A.D.A. (Americans With Disabilities Act) requires that the employer provide you with 'reasonable' accommodations--that means that the employer has the ability to evaluate and make decisions about what accommodations they can and what accommodations they cannot provide you with. If, for example, the company frowns on telecommuting
and does not allow it for others, for them such an accommodation may be unreasonable. I tend to agree with you that it appears to be a fairly innocuous accommodation unless you really have to be 'hands-on', but that is generally at their discretion. Hence, lowering your salary if you work less is not inherently retaliatory.
You could consider filing suit, but it is not a clear-cut case and not a very easy case to prevail under, at least based on your facts. If they would have cut your hours if you work at home BUT remain working for the company with the same schedule, my answer to you would differ, but as you are now technically working less, they can reduce your salary to that level.
Hope that helps.