BOSTON (AP) — Lawyers for a Massachusetts man charged with trying to help al-Qaida challenged the credibility of a friend who testified that the man encouraged him to watch jihadist videos and read publications promoting violent jihad.Prosecutors say Tarek Mehanna traveled to Yemen to seek terrorist training. When that failed, he returned home to Sudbury and allegedly began translating and distributing materials promoting terrorism.On Friday, Mehanna's lawyer cross-examined Ali Aboubakr, who testified a day earlier that Mehanna referred to Osama bin Laden as "my real father" and praised the Sept. 11 terrorist attacks. Aboubakr said he did not always hold the views expressed by Mehanna but went along with them because he wanted to "get his approval."During cross-examination, Aboubakr acknowledged that he also admired bin Laden and had purchased books on jihad and watched jihadist videos on his own. He said that although he, Mehanna and other friends often talked about jihad, he did not consider them a terrorist cell.Mehanna's attorney, Janice Bassil, peppered Aboubakr with questions about the online chats the two men had in 2006, when prosecutors allege that Mehanna was trying to promote violent jihad.Aboubakr acknowledged that he admired Osama bin Laden and was not pressured to do so by Mehanna."He wasn't influencing you — this was something you felt?" Bassil asked."Yes," Aboubakr replied.Aboubakr said several times Thursday that he feigned interest in certain subjects because he wanted to impress Mehanna. Bassil suggested that it was only after Mehanna was charged and Aboubakr was questioned by authorities that he decided to say he felt a need to impress Mehanna by agreeing with him in his desire to wage jihad against the United States.On Friday, Aboubakr said there were times he saw Mehanna as his "educator." But he also acknowledged that he told a grand jury that he did not believe Mehanna was trying to teach him."It's only today, after you got that summons ... that you're saying, 'Oh, I did this because I wanted Tarek to like me,'" Bassil said."No, this is not the first time I felt that way," Aboubakr replied.Aboubakr was the first of several friends expected to testify against Mehanna under grants of immunity.Both Mehanna, 29, and Aboubakr, 25, are American-born citizens from wealthy Boston suburbs.Aboubkar testified Thursday that he and Mehanna would chat online and watch videos at Mehanna's home. He said one video showed the beheading of American businessman Nicholas Berg in Iraq. Others showed suicide bombers.Mehanna's lawyers deny he was promoting terrorism and say he was exercising his right to free speech when he expressed his anger over the U.S. invasion of Iraq. They say he visited Yemen to find religious schools.Testimony is scheduled to resume Monday.