Leading the witness is the exact offence they claimed Mark Lane was doing with witnesses, Marks rebuttal was that is exactly what a lawyer for the defence does, not the prosecution.
Since Lane is a lawyer, albeit a dishonest one, I'll presume that he actually knows the rules regarding leading questions and so you're simply misquoting him -- just as you misquote so many others.
The allowability of leading questions has nothing to do with being a defense or prosecuting attorney. Leading questions are disallowed in
direct examination, that is, questioning a witness you called for your own side, because it can seem too much like "coaching" the witness to give you the answers you want.
But leading questions are perfectly acceptable during
cross examination, i.e., when you're examining a witness already called and questioned by the
other side. He is presumed to be hostile or antagonistic to your case and therefore unlikely to allow himself to be "coached" to the answers you want.
Both the prosecution and the defense can call witnesses, forcing them to appear (having the judge issue subpoenas) if necessary. Both sides are entitled to cross examine the other side's witnesses, using leading questions if they wish.
Most witnesses are willing to help the side that calls them, but not always. For example, a prosecutor might call a friend or relative of the defendant who, for obvious reasons, would prefer not to testify against the defendant. But unless the witness qualifies for one of several specific privileges (spousal, attorney/client, doctor/patient, priest/penitent, etc) or invokes his Fifth Amendment right against self-incrimination, he
must testify. The court can even toss him in jail temporarily for contempt until he does. (Even if he invokes the Fifth, he can still be compelled to testify if he is granted immunity from prosecution for his compelled testimony.)
Since few witnesses are willing to go to jail to avoid testifying, it's more likely that they'll simply drag their feet on the witness stand. If the attorney who called them is unhappy about it, he can ask the judge to declare the witness "hostile", meaning that he can conduct his direct examination of the witness as though it were a cross examination -- including the use of leading questions.
10 years ago, a San Diego man named David Westerfield was accused of kidnapping and murdering a 7 year old girl. One of the major prosecution witnesses was Westerfield's son, who was obviously quite unhappy with the idea of testifying against his own father. But there is no parent/child privilege, so he had no choice but to help convict his dad who was in fact sentenced to death. I don't remember if the prosecution actually asked to have the son declared a hostile witness, but it seems likely.
Note that
leading questions are not
loaded questions. A leading question is one that merely suggests the answer: "On November 22, 1963 at 11AM you were in the Texas School Book Depository Building, were you not?" A
loaded question is one based on an invalid or improper premise. The all-time classic example is "When did you stop beating your wife?" Leading questions are okay in examining a hostile witness; loaded questions are never OK in any type of examination.