Both BU (or, rather, "Emergent Consensus") and SegWit needs significantly more than 50% support to "win". Forcing through SegWit or bigger blocks without sufficient miner and community support may cause a chain split, which may be very harmful indeed. I find it particularly weird that those who have been arguing loudly that the protocol shouldn't be changed without "full consensus" and that a hard fork is dangerous due to the risk of a lasting chain split now seriously want to force through segwit at the 1st of August, come hell or high water ... it just doesn't make any sense to me.
Now there is the compromise segwit2x, that's my favorite proposal for the time being.
I also hope that the proposal of SegWit2x go forward as it may rescue Bitcoin from it's current crisis... Indeed its very explanatory article @tobixen i like your post in the blog