Warning! Spoilers ahead for Young Sheldon season 6, episode 12. season 6 features a small but important detail that reveals Sheldon's true feelings about Howard in . Despite Sheldon's lack of social skills, he found a great group of friends in Pasadena. While he appreciated them, he also tended to mock them mercilessly, especially regarding their academic achievements. However, Sheldon didn't invalidate and ridicule anyone as much as he did Howard.
in as he battles it out with East Texas Tech about his grant database. The episode "A Baby Shower And A Testosterone Rich Banter" offers the boy genius a change of pace when he is forced to hang out with his family at home for Mandy's baby shower. This allows Sheldon to relax, as reflected in his casual outfit which also hints at his true feelings about Howard in .
Since adapting his layered shirt aesthetic, Sheldon has made it his signature home outfit. He wears the same style as he hangs out with Georgie and Mandy's brother in , episode 12. However, he sports a NASA shirt, suggesting that the space organization holds some importance to him. Between this and the boy genius wearing an astronaut costume in a previous introduction video hint that he had childhood dreams of becoming part of the civil space program. So, to mask his envy of Howard, who worked for NASA and was sent to the International Space Station, Sheldon mocked his friend instead.
Granted, while Sheldon loved looming over his friends and making them feel like he was superior to them, he always zeroed in on Howard. Since he lacked the emotional maturity to process unsavory feelings like envy and jealousy, he resorted to masking them by being extra cocky to make himself feel good. However, there were times that he just tried ignoring them, including when Professor Proton died. Luckily for him, , was aware of what was happening and guided him throughout the ordeal.
expounds on 's reason why Sheldon hates Howard, and it has something to do with him also being an engineer. As it turns out, the boy genius had a very bad experience in his freshman engineering class as it was the first time he felt inadequate in academics. Somehow, this added to the idea that Sheldon was already envious of Howard's opportunity with NASA, which further grated the socially-inept genius. Luckily for him, Howard never really took his tirade to heart and still chose to be friends with him.