The way some of the posters were expressing themselves, it came across sounding like the entire Lag BaOmer was being pushed off to the next day. When people talk about “pushing off Lag B’Omer”, they are referring specifically to the bonfires which they wanted to be pushed off (either to daytime or the next night – I’m not sure which).
Some people think that it’s not a big deal – there is no chiyuv to light a bonfire on Lag B’Omer, so why not push it off if it might cause Chillul Shabbos.
However, the counter-argument is that some people (I think certain or all Chassidic Groups) have a very strong minhag concerning lighting bonfires on the night of Lag Ba’omer. It’s not just a “fun thing to do” but a very real part of their religous practices, and they do consider it a serious thing to push it off. And they don’t feel that they should change their minhag for the sake of people who don’t keep Torah and Mitzvos who would have been mechalel Shabbos anyhow and who don’t have to be mechalel Shabbos for the sake of the bonfire (if they were Shomer Shabbos, they would just spend Shabbos in Meron. The reason they aren’t is because they aren’t shomer Shabbos anyhow and they would be mechalel Shabbos either way).
Someone I know had the argument that it’s no different than people going to the Kosel on Shabbos which causes a need for security forces who are also mechalel Shabbos (by driving in on Shabbos, etc.).
I’m not taking sides here as I don’t feel qualified to do so. I just think that it’s important for people to realize there are two sides to the issue and they shouldn’t be so quick to judge. There are probably other factors involved that I don’t know about which is even more of a reason that no one should be judging.
Regarding the Boyaner Rebbe pushing off the bonfires to 3:00 AM, I’m not sure if that was what the Rabbanut was calling for originally. They may have been asking that no bonfires be lit at night at all, and that may be what people were taking issue with. In the above article, it mentions 4:00 AM. 4:00 AM is not 3:00 AM. 4:00 AM is practically daytime halachically, and perhaps they were concerned that by the time they really start, it really will be daytime.
So 3:00 AM may have been a compromise position on both sides.