Paul McCartney was used to John Lennon's negative comments in the press by the 1970s. In the 1960s, though, he saw them as a threat to The Beatles.
After The Beatles broke up, Paul McCartney got used to reading John Lennon’s negative comments about the band in the press. He attacked their music, his former bandmates’ solo projects, and, often, McCartney’s personality. While the group was still together, though, any negative comments made by Lennon had the potential to hurt them. When McCartney read some of Lennon’s remarks about Apple Records, he lashed out at the journalist who recorded them.
Source: Emma McKee/cheatsheet.com