You do encounter a bit of judgement like that on-line - I have noticed it on this forum sometimes sadly.
I have, however, NEVER actually encountered it in real life. Many people get divorced these days, and almost all of them go on to pursue new relationships at some point. It's very rare to find somebody who just devotes themselves entirely to being a parent - and if they do, that is quite often because they just can't be bothered with relationships any more.......
You are quite right - you are entitled to a life of your own. I find it really quite concerning when people expect their children to become their whole life and reason for existence - what an enormous amount of weight for those children to shoulder!
And most of us have needs - for sex, for romance, for physical affection - that our kids can't meet. So for many of us dating is, if not quite an essential, pretty high up there on the having-any-quality-of-life requirements list. Not for everyone, obviously. But for many.
Of course dating with kids is different - your kids will always be your priority, and it does put some limits on what you do...... But it's also entirely possible.
I think what REALLY grates on me is when the judgement is solely aimed at women. People who wouldn't question a father's right to date again, but if a woman does it she must be some kind of wild hedonistic nymphomaniac....