I see Lydecker as violating personal boundaries by meeting MacPherson in the nude in the bath. He's trying to put MacPherson back on his heels and in his place. When he gets out of the tub and asks MacPherson for a towel, he's putting MacPherson into a subservient position. Lydecker is communicating to MacPherson that he considers him beneath him, so far beneath him that he feels comfortable being nude around him like would around a servant. (Lydecker has servants, since someone must have let MacPherson in.) Strangely enough, the bath scene is a dominance play IMHO.