Recently, one Hillel (the Swathmore campus Hillel) voted to call itself the 'open Hillel' and to allow such participation.
Supporters of the Hillel at Swathmore have accused the national Hillel foundation of being hypocritical in opposing the ASA boycott while undertaking a boycott of their own.
For Hillel not to be hypocritical, there must be substantive difference between the two cases, and, there is.
1. The ASA policy bans all Israelis, whatever their belief, whatever their academic merit, whatever the topic of the presentation or paper. The national Hillel policy bans only individuals.
2. The ASA policy aims at a highly tangential population and seems odd on its face. After all, how many Israelis are even interested in American studies. The national Hillel policy bans a group that is much larger (a lot of anti Israel groups are on American campus).
3. The ASA policy seems to single out Israel and, in fact, their boycott policy falls under the national Hillel policy (which dates a few years before the ASA boycott). That is, the national Hillel policy mentions boycotts and those with double standards (the ASA doesn't seem to acknowledge that some groups are discriminated against other than Palestinians).
Thus, I don't think Hillel can be fairly called hypocritical in this case.
Notwithstanding that, I personally, don't understand the national Hillel policy. It seems to me that national Hillel ought to allow, on a case by case basis, supporters of the boycott, those with double standards, etc. to address Hillel if such persons are otherwise of good will.
The open Hillel policy is here.
The national Hillel policy is here.
Information on the ASA policy is here.
A NYTimes editorial following a NYState Legislature action is here