That whereas the ANC (according to Mandela's words above) only resorted to force after alternative means of resistance had failed, the opposite is true of the Palestinian factions - they have only adopted alternative means after force has failed. From the first national uprising in 1936 until the PLO's apparent renunciation of violence 52 years later, force was regarded as the
only legitimate means of liberating Palestine by the dominant Palestinian players, and still is by the faction running the Gaza Strip. Now you may regard the distinction as unimportant, but clearly Mandela felt it worthwhile stressing the chronology of the nature of resistance to Apartheid, since, I presume, he recognized that it had a bearing on how that resistance, and the South African government's response to it, was understood.
The conversation above was related to events surrounding the second intifada, while the Mandela quote was a more general statement of principle relating to the entire movement against Apartheid. I'm not someone who denies that the Palestinians have a right to fight for their rights (including their national rights), by force if necessary (although I think their use of violence has on balance been counter-productive over the years, the 1936-1939 uprising, the 1947-48 war, and the 2nd Intifada being the primary examples). I'm simply arguing that the Palestinians have agency, and that the particular form their struggle has taken over the decades is relevant to understanding Zionist/Israeli behavior and actions and, by extension, the way the conflict has played out, however asymmetrical it may seem (obviously the reverse is also true).
For what it's worth, I think the kind of protests we've seen recently in Gaza could be a potentially positive step in Palestinian measures, one I've been looking for since the 2011 protests. If they can evolve into a pan-Palestinian phenomenon encompassing Palestinians in the West Bank, Israel and the Diaspora as well as Gazans, if they can shake off the control of Hamas, Fatah and the other armed factions to become a properly grass-roots movement, and if they can rebrand the message as something more reasonable than "we're coming home to oust you off our land" (since we're discussing the South Africa analogy then perhaps they should take a look at the
ANC's Freedom Charter for an example of how to do it), then that could possibly be a game-changer - I wrote this in 2014 on this very topic -
https://www.redcafe.net/threads/israeli-palestinian-conflict.306471/page-178#post-16675517