Last Second Foul

[Wondering]

Team A is leading by three points with 10 seconds left in the game. A1 has the ball and is part of a two-on-one fast break.

As A1 crosses the midcourt line he accelerates past the last defender B1. The lead sees B1, who is now behind A1, reach around from behind A1 and try to slap the ball free - somewhat hitting A1's arm in the attempt.

The lead notes the ball was not dislodged and A1 did not seem to be affected (put at a disadvantage) as he accelerated for the lay-in which basically put the game out of B's reach.

B is screaming: "Why didn't you call a foul on us and stop the game? We didn't want to clobber A1!"

The lead had been taught to "see the whole play" and not unneccessarily call fouls that would kill a fast break.

My question is: Should the lead have ignored a minor-to-medium foul at midcourt that seemed not to affect the fast break and thus allow A1 to reap the benfit of superior speed and play.

Or should the lead have called the foul - realizing that B was trying to stop the clock & lay-in with a foul but did not do a very good job of it - not wanting an intentional foul or to injure anyone?