The gemara tries to figure out the case where one violates avoda zara "b'oneis" and the consequence is that the item assumes a status of being worshiped. In the course of the discussion there are three issues which arise for avoda zara that is worshiped by force: a. is it permitted? b. even if not permitted, does one deserve capital punishment for violating. c. what is the status of the item that was worshipped?
1. Rami Bar Chama suggests that the case of being forced to commit avoda zara would be where Reuven forces Shimon to worship an item belonging to Shimon. Tosafos explains that we are speaking where Reuven is holding a gun to Shimon's head and threatening him. We would then consider the act of Shimon to be serving avoda zara, just that it is by force. However, if Reuven was physically pushing Shimon down to bow his body in front of the avoda zara, we don't regard Shimon as doing any action at all and therefore don't require a pasuk that exempts o'neis to explain why the item doesn't become assur.
2. Rav Zeirah rejects this based on the concept we learn out from a girl being raped - ולנערה לא תעשה דבר - because the Torah exempts for o'neis. The gemara is assuming that just as the worshiper wouldn't deserve capital punishment for a crime he committed by being forced, the item wouldn't assume a status of being worshiped (and assur as a ne'evad).
3. Rava answers that we find a distinction between private and public. Tosafos explains that Rava seems to be throwing in extra information by following an opinion that one must give up their life for avoda zara if he is being forced into a public violation but not for a private violation. This doesn't seem to directly address the problem raised by rav zeirah. Rav Zeirah asked his question based on the assumption that one should have to sacrifice his life even for avoda zara being committed privately, yet since he wouldn't receive capital punishment, the avoda zara shouldn't become assur. Rava doesn't seem to be addressing this issue. Tosafos explains that Rava is trying to make the braisa work even according to the opinions that one must only give up their life for public violations, not for private violations. However, Rava's answer is really just undermining the premise of Rav Zeirah. Rav Zeirah assumed that the status of something becoming assur as avoda zara should be dependent on whether he deserves capital punishment. Rava disagrees and holds that it is dependent on whether the person was allowed to violate - if it was assur to violate then the item would assume status of avoda zara, even though he isn't chayev misah.
The gemara assumes that when Reuven forces Shimon to worship avoda zara, the item becomes assur since shimon should have given up his life and avoided worshiping the avoda zara. Meaning, we regards shimon's act to be an act of worship, just that he was forced to do the act. The difficulty with this approach is that by definition avoda zara entails the acceptance of the item as a deity. If Shimon is forced into worship, he doesn't even regard the item as a deity. Rather than exempting Shimon because of "o'neis", we should exempt him for not doing avoda zara. Furthermore, since this doesn't qualify as avoda zara, the item worshipped shouldn't become assur - why does it? The gemara seems to hold that both in regard to the obligation of the worshipper and even in regard to the item worshiped, we disregard the intention of the worshiper and merely look at the appearance of the act. So long as the act looks to the naked eye as avoda zara, we consider the worshiper to be doing an aveira and even place an issur on the item worshiped, despite his intentions of not accepting it as a deity.