The justices argue that the town council determining what should and should not be in a non-denominational prayer, or them drawing up a rotation between various faiths according to some particular system, would have been much worse in terms of violation of the separation of church and state than the actual procedure, which was more random and haphazard, and limited to Christian invitees mostly just because there are almost no non-Christian places of worship within the city limits.

And really, I do agree that it's a stretch to talk about being "forced" to participate - there were many references in the opinion to a prior decision about a high school graduation ceremony, where the SC did feel that it was difficult for graduating students to reject the religious elements, and did rule against the school for "forcing" its students. In here that seems like a stretch - people who had a problem with the Christian prayer, or for that matter the possibly more numerous Christians who had a problem with that Wiccan prayer that one time, could just ignore it, or go outside for a bit.

The French "laicité", the aggressive enforcement of removing religious elements from public and political life as much as possible, is one possible solution, yes. I don't think it's the best one, though. I think the justices are right when saying that an attempt to intentionally find a balance between religions - taking into account the very small numbers of Muslims, Jews etc. in the town - would probably have been worse than what they did. They could have avoided the whole problem by canceling that prayer altogether, but that seems like overkill considering that there wasn't much in the way of protest from the citizens, and when there was, they did react in the way they should by allowing the other religions to be represented, still in the same haphazard fashion that didn't require any actual judgement calls on which religions to invite how much.