Well first of all, it's not really "hate". Theyre just not fond of eachother.
In the latest video Tord posted about Edd's death and why he left Eddsworld on YouTube, he states that shortly after Dudette seguinte Door, Edd had some technical issues. So he was using an Internet Café. He left Tom and Tord with eachother for a bit, and they found out that they're not really fond of eachother.
They are good friends I heard… just off screen. They didn't like eachother very much, because they called eachother offensive names. Tord called Tom a "Jehovah's witness", and Tom… I forgot what Tom called Tord…
They don't hate eachother. They basically had the same relationship as they did with everyone else in the show. For instance, when Tom went all IN YOUR FACE TORD, IN YOUR FACE!, he probably would've done that to anyone else. Tord said himself that Tom had a very little effect on him leaving the show.
At some point Edd had computer problems and it caused tom and tord alone. After talking they found they don't really like each other too much XD. In the show they call each other names like... Idk I can't remember
They don't hate each other, they're just not friends. In real life they're never seen fighting, probably because it's cut or they just don't fight. In ZantaClawz I, Tord didn't do anything bad to Tom and neither did Tom, or, at least that's what I remember last. But in my mind, they don't hate each other, they're just not friends.