Whilst I detest any form of bullying or vitriol, and totally agree with you op that debate should be objective and respectful, I think that the behaviour of this last government and the way they behaved, and certain Conservative politicians, Boris Johnson being the main offender, stirred up a lot of frustration and anger in the general public and in those who are politically engaged.
Owing to Conservative lies and their asset-stripping of the country, their corruption, their hollow promises, and Johnson using an important issue like Brexit as simply a means to promote his own career, which he then proceeded to play as a game without values, integrity, or any idea of service to the country, I think people have become justifiably angry and upset.
We saw it in yesterday’s election how fundamental social inequalities, lack of decent public services, lack of opportunities for the young, how not having a sense that you have any control over your own life circumstances, make people opt for more “vitriolic” ideologies in the shape of Reform, which are very black and white and extreme, divisive, and lacking in nuance, or respect for consensus.
Contrary to your argument op, many of the televised Brexit debate that I watched, sorry to say, but as a very general observation, it was the opposite of what you are describing, and it was the Brexiteers who were heckling and insulting, and Remainers who were trying to maintain a degree of civility.
Another factor is that our leaders and those who should know better, have set a very poor example, and as a result we have lost faith in our institutions which makes everyone feel more insecure, frustrated, and powerless.
Lastly, some elements of the left are very passionate, simply because they have traditionally been the stamping ground of the young and idealistic. It’s normal for people to then experience the realities of life, encounter opposing views, and come to terms with what is possible, and temper their arguments accordingly. But that is more about youth than ideology.