Veil and Silence fill a similar role. Discard is "protection" but interacts differently and stops different problems. It's proactive, live as early as turn 1, protecting us under a different axis than Veil and Silence do. That's why the URwb and URgb builds splash black for Thoughtseize. It's something unique green and white can't do.
IT and ETutor function very differently. ETutor is cheap and instant but can only find some card types, is card disadvantage, and only goes to top of library. IT puts the card in hand immediately but is slower to use and requires an enabler (LED or play out hand). ETutor forces some suboptimal card choices so that they're tutorable, while IT doesn't restrict the rest of your deck design.
While both are "tutors" and "protection", the way they accomplish that has very different impacts on how the deck plays out vs an opponent. IT is more replaceable because all of the tutors have some drawback, but Thoughtseize is something no other color can do.
Silence doesn't scare off discard. If you want to maximize Veil to scare off discard, why not just play RUG with 4 Veils?
Discard hurts because we have to sculpt an A+B+C combo with protection. We can't cast Breach until the combo turn, so we need to keep Breach and protection in hand. Discard disrupts that. Discard hurts Jeskai even more because it lacks card advantage and has multiple sources of card disadvantage (FoW, ETutor, Silence).
How to answer this? The RUG build has less card disadvantage and has Veil, so it isn't hurt by discard as much. Jeskai has advantages in other matchups (especially storm mirrors) but RUG does better in attrition games.
Another option is Michael Keller's list above playing
Dark Confidant to get back card advantage. Bob is smart. Our curve is low and, unlike ANT, we don't care about life total. I wonder if Bob is better in transformational SB (after they board out removal) instead of maindeck in game 1, when it will eat 100% of removal.