When I've been caught up in the chaos the "viewers" are, as you say, people who've heard that "der flyin scotsmann train" is passing by and have decided to go and dribble because it's "faymuss, innit". I wouldn't class any of them as railway enthusiasts. I doubt many of them would even be able to tell the difference between the Scotsman and a fully-streamlined LMS Coronation if it was carrying a "Flying Scotsman" headboard.
Last time I got involved with one of the Scotsman "visits" every access point along the route in my bit of the world (that's every platform, every road level crossing, every foot crossing, every user worked crossing, every staff gate) had to be staffed to try and keep the idiots under control. That took a ridiculous number of Network Rail and TOC staff and contractors away from their day jobs; Network Rail Ops Managers, P/Way, S&T and other NR staff were stuck arguing with entitled idiots at trackside access points, and TOC staff, cops (BTP and civvy) along with contract security guards were dealing with the same issues at stations. Every single member of staff out dealing with that train had other work they should have been doing but which had to be deferred just so they could help deal with the Scotsman-luvvies.
It was a hugely disruptive (and of course expensive) operation just because one specific steam loco was pulling a train. How can it be in any way sustainable?
It's certainly not necessary to ban all steam movements, but Scotsman is simply causing a disproportionate amount of disruption to the network, and it simply can't go on like this. I'd pull 60103 off the national network completely.