I know that my Heart interter on my Sabre would go crazy when a marina neighbor "tested" his SSB.

The RFI of broadcasting impacts a variety of electronics on board. Sometimes I believe it is from the simple "over pressure" of the boardcast signal. I think it really depends on your piece of equipment and the "antenna" that exists variably within your boat which may back-feed equipment.

As for the "ground" being the culprit, I'd not assume that this is the simple answer.