When Tom shows up with some of his friends on horseback, Gatsby is asked to join them. Through the course of the conversation, Gatsby informs Tom that he has met his wife (Daisy) before. Tom is suspicious and wonders where he's met Daisy before. When Gatsby leaves, presumably to get his car keys, Tom remarks:
I wonder where in the devil he met Daisy. By God, I may be old-fashioned in my ideas, but women run around too much these days to suit me. They meet all kinds of crazy fish.
This is hypocritical because Tom "runs around" too much as well. He is having an affair with Myrtle. According to Tom's logic, he would be one of those "crazy fish." Tom is even quite open and even proud of this affair - with some people. In Chapter 2, he takes Nick to meet Myrtle as if to show off his ability to do whatever he wants. In his narrow-minded views, Tom accepts the double standard that women should not "run around" but that it is okay for men, namely himself, to do so.
When Tom finds out that Gatsby knows Daisy, he is disturbed by this fact. Tom is a jealous and hypocritical man. He has issues with Gatsby and it is clear that Tom lacks control at this moment. After Tom and his friends meet Gatsby in Chapter 6, Tom is quite judgmental about Gatsby and wants to make his friends think that Daisy and other women shouldn't be allowed to go out on their own.
"I wonder where in the devil he met Daisy. By God, I may be old-fashioned in my ideas, but women run around too much these days to suit me. They meet all kinds of crazy fish."
Tom is the biggest hypocrite of all. He makes this statement to his friends to make himself look like the kind of guy who treats his wife well, but in reality he is the one who is running around. Tom is having an affair with Myrtle, yet is questioning how Daisy met Gatsby. Tom is saying that women shouldn't go out on their own because they could meet some crazy people, but he is the one who has gone out on his own and met someone crazy. The twisted way Tom thinks life should be leads to tragic circumstances for all involved.