AV is legitimately as bad as FPTP. The only good thing is that you can point to first round results to show what the country thinks without tactical voting; except tactical voting can still happen. I'm just going to reference Roger Mortimore here:

Consider the simple case of a constituency of 60,000 voters of whom 25,000 support Labour, 20,000 support the Tories and 15,000 support the Liberal Democrats. Let us assume that these people are distributed on left-right ideology scale with Labour voters on the centre-left, the Liberal Democrats grouped around the centre and the Conservative voters on the right

Under first past the post this would be a Labour seat. But under AV whichever candidate comes third will be eliminated and their voters’ second preferences will be redistributed between the remaining two to see who wins. Given the set-up above, then Labour and Tory second preferences will split overwhelmingly in favour of the Liberal Democrats rather than to each other. But Liberal Democrat second preferences will split pretty evenly between the other two parties – let’s say 7,000 to Labour and 8,000 to the Tories.

So put yourself in the position of a Conservative voter whose main consideration is to stop the Labour candidate winning. If the Conservative candidate finishes second and qualifies for the final count, then the Liberal Democrat voters’ second preferences will split as above, boosting the final votes for the other two candidates but otherwise not affecting the final result. Labour will still win: