Now the Not For Sale coalition of supporters groups and fanzines is urging fans to attend a public rally at the Apollo Theatre in Ardwick on Bank Holiday Monday (3pm).
Supporters' fears were heightened this week by plc chairman Sir Roy Gardner's revelation that the United board has repeatedly asked Glazer for assurances that Sir Alex Ferguson's transfer budget will not be cut, that ticket prices will not soar and that debt levels will not reach unsustainable levels.
Glazer has not responded to the request - or the question of the possible sale of the ground - and has pressed ahead with a business plan that the board has in the past described as "aggressive" and "damaging".
Now United supporters opposed to Glazer claim that this week's final offer document has revealed "the full horror" of his plans for the club.
Andy Walsh of the Independent Manchester United Supporters Association will chair the rally at the Apollo and is urging supporters to give their voice to the campaign.
He said: "We cannot say too much about the detail of Glazer's offer document for legal reasons, but it is fair to say that the whole future of the club is at stake. We face not only the possibility of the team being starved of transfer funds, but of the current stars of the team being put up for sale to pay for Glazer's acquisition.
"His refusal to give any assurances to the board, to the manager or to the supporters, once he takes the club private, shows that.
"United's assets are its players and its ground and under Glazer's plan all of those assets are under threat of sale."
The Not For Sale group will outline its latest strategies for fighting Glazer at Monday's meeting and among those present will be Manchester Central MP and United fan Tony Lloyd, Shareholders United chairman Nick Towle and football business journalist David Conn.
The Not For Sale group is stepping up its boycott of United's sponsors and commercial partners by setting up "teams" of supporters, each of which will have a specific target.
Details of SU's expected legal challenges to Glazer's takeover, and ideas of how ordinary supporters can get involved will also be discussed.
As part of the boycott campaign, a skip will be placed outside the theatre for `N!ke amnesty'. Supporters will be asked to dump any clothing or footwear they have which was made by the sportswear giant - United's biggest commercial partner - for re-distribution to Third World charities.