Some of my bestfriends are homeless people! Maybe not really "best friends" but theres a handful I know that frequent the local park here. (read: they're there all day every day for the most part) and I almost always drop by and see how they are doing. I like hanging out with them because they know what hardship is and they don't judge other people nearly as much as those who don't. That being said, I've run into a few different types of homeless people that are arguably so different from one another that I can see why certain people have bad perception of the homeless population.
Let me use this guy I know, Bert, as an example. He's homeless. He doesn't really have any marketable skills and his past is shoddy enough with all his arrests and other red flags that would make employment difficult for him. He can't shower daily, he can't wash his clothes on a regular basis, that alone is enough to bar him from getting any decent job. He also quite a few arrests for public intoxication among other things. That all in the past though, he doesn't drink anymore and is something like 2 years sober. He smokes a little pot, but does that really hurt anyone? He is respectful about it. He doesn't do it out in the open where everyone and their children can see. He doesn't sit on a corner flying a sign begging for money so he can just go buy cigarettes or something like that like the majority of the other homeless people do. He'll occasionally ask people he knows if they have any spare change(but only people he knows) or ask someone to spare a cigarette if sees them smoking. If they say no or that they don't have any, he leaves it at that. He doesn't follow them around and pester them about it or give them longing glances that are saying, "I KNOW YOU'RE LYING" he just simply moves on. His day is mostly filled with playing cards and playing on a gameboy that someone has given him. I always try to bring him food when I can and give him change when I can--sure I might be enabling him to live this lifestyle and not to actively seek a job, but I can't really blame him for not putting a lot effort forward in that regard when he already has too much against him for something beyond his control.
Then there is this other one I know named Bob. You can rightfully call him an alcoholic, and he'll agree with you. He's a cool guy as a person, but I absolutely despise him as a homeless person. He CHOOSES to be homeless. He CHOOSES to fly a sign and then go and spend that money on alcohol cigarettes etc. While he is a cool guy and always shares the money that he gets from flying his sign, I don't think he should be doing that in the first place, especially given what he spends the money on. That being said, he is also more or less respectful like the first guy, Bert. He leaves you alone after you tell him no and that's all there is to it. He might get a bit rowdy with people he knows when he a little drunk, but never with people he doesn't know. He also is generally pretty honest when it comes to asking for money, its not like he has "Hungry and Homeless" on his sign trying to con people into feeling bad that he hasn't eaten when he is just really going to spend it on alcohol. He's still young(like 24) so there is a lot of opportunity for him if he decided not to get drunk all day every day.
THEN there is the people like Dave. An old veteran who gets like 800+ dollars in social security income. He's homeless because he spends it all on alcohol, cigarettes etc. He doesn't fly a sign, but he also doesn't need to. As a veteran, there are a lot of benefits for him that he could seek out to not be homeless. But he just spends all his money on alcohol and etc. He gets EXTREMELY confrontational when drunk to anyone that he thinks even so much as looks at him the wrong way. He makes demands of everyone with the line "I'm a veteran and I'm homeless and this how you thank me and blahblahblah." When sober he's a cool guy which is why I'm glad he's actually recently quit drinking and is better appropriating his money.
Then there are people who are like Dave named Justin and Ali. They are extremely annoying. Early twenties. Fly a sign all day. Complain they didnt make enough money. Complain how everyone is rude to homeless people. Complain that people aren't doing enough to help them out. Complain. And complain. and complain. And complain. They are extremely confrontational at all hours of the day regardless of however much alcohol they have consumed or anything of that nature. They feel entitled to everything because "they're homeless and need the help" yet don't ever want to do anything to actually earn their keep. They like to boss people around and tell everyone how they should/shouldn't act while generally making no positive contributions to those around. This is in great contrast to the first two I mentioned. Bert, for example, tries to always earn his money if there is a way he can. Bob doesn't so much, but he always shares what he has and doesn't make demands of anyone.
It these last 3 people that give the homeless a bad name. All in all, they're people just like you or me. Treat them like a person and you'll be amazed at how human they actually are. Treat them like a pariah who's worth no more than the dog shit on the heel of your shoe and you'll see just how nasty they can get. It's largely hit and miss with many of them, but you should at least give them a chance I say.