An assertive person could easily say, firmly and with confidence, that "I don't have an opinion on this topic, because the evidence isn't definitive." If you can't do that, then there is something in your scenario that's incompatible with intellectual honesty, but it's not assertiveness -- more likely, it's a feeling of needing to satisfy the expectations of others that you will have an opinion. That feeling is like antimatter for intellectual honesty, but it's totally different from assertiveness.