While the factors causing so much negativity are much as you describe I would suggest that the "anti" feeling was as much from senior civil servants in the appropriate departments (Treasury and Transport) as from elected representatives. For all that many vilify Thatcher in the end, despite her personal disinterest in railways, she decided that BR was best left alone. The mess of privatisation was more due to Major's determination to leave a political legacy even to the extent of ignoring his own advisors on the best way to proceed.
You may well be right, but...
The impression I gained at the time (possibly from frank remarks made at the time by politicians) was that one of the motives behind Thatcher's liberalisation of coach licensing (remember British Coachways?) was that a privately owned express coach network would not only wipe out the (nationalised) National Express network but also have a very destructive effect on British Rail's passenger business, leaving it so weakened as to be easily disposed of. In other words, I think she did 'leave B.R. alone' - but left it to die! For example, I remember immediately after de-reg that there well over a hundred commuter road coaches running betweenLuton/Dunstable and London daily - although the dispute about the original Bedford-St Pancras units (the 317s) and the resulting unreliability of the service was also a factor. But it didn't work long term, except some of the successful TOC franchise bidders were bus companies.
An erstwhile colleague* had been, before I worked for him, the Chairman's bag carrier and purchaser of sandwiches( etc.!) for breaks, during the 1982 ASLEF flexible rostering strike negotiations. He was clear that it was Thatcher's direct orders that B.R.
must not concede anything at all to the drivers. However, she then suddenly became aware of the grievous effect on the economy of no-one being able to get into City offices, so issued a very swift 'get them back to work
NOW' instruction. Of course, to do this instantly could only be achieved by total capitulation. Result; great bitterness by BR management that the opportunity for any negotiation was thrown away by Thatcher. And she certainly did a U turn!
*the manager I mentioned was one of the best Inworked for, and soon went on to greater things. He became MD of Merseyrail but very sadly died at a very early age about 25 years ago of a medical condition that was, I think, congenital.