Final answer:
Matt finds Mr. MacGregor repulsive because of the evil traits inherited from his ancestors, causing an instinctive repulsion. McTeague's poor understanding of these hereditary influences and other relational tensions contribute to his feelings of unease and repulsion.
Step-by-step explanation:
Matt finds Mr. MacGregor repulsive due to the inherent hereditary evil that shapes MacGregor's character. This evil is described as being the result of the vices and sins of his ancestors, tainting him and flowing in his veins. Despite not desiring this and not being to blame, Matt is affected by the foul stream of inherited traits, and this dynamic creates a visceral repulsion.
The complexity of the issue is further complicated because Matt, or McTeague, struggles with comprehending the reasons for his feelings, leaving him to confront these hard-to-grasp aspects of heredity with just instinctive resistance. Additionally, Marcus's change in behavior towards McTeague, shifting from friendship to a sort of uneasiness and eventual aggression, adds to the tension. McTeague's inability to relate to women, his insecurities, and the general sense of discord he feels about life after a woman enters it, contribute to his disquiet and repulsion towards individuals like Mr. MacGregor.