due to not knowing enough about what I'm talking about. 
Ok, started as a discussion on FB, where one of my FB friends, who is also my niece's fiance wrote a status claiming all single mums are nothing but feckless scroungers who live off of benefits and are bleeding the country dry
, they should all get a full time job or be made homeless and if they die homeless, he'll be happy, because it's one less scrounger to pay for. This is because FB friend is totally pissed off with working over 50hrs a week in 2 jobs to support these lazy breeders. 
This particular FB friend has written other equally offensive statuses but I either ignore, or they don't escalate.
Anyhow, I posted on this one after he received lots of 'likes' and 'well said mate' to ask why the onus is always on the single mums, basically told him what a load of old clap trap he is talking, and maybe the focus should be on the father's who dont pay for their DC, and surely if a single mum gets a job, she will still have to claim benefits in the guise of tax credits, housing benefit etc, because wages aren't high enough to support a family. Anyhow on and on it goes, covering topics such as single mums only have DC to get a council house and live off of huge
amounts of IS, which I don't believe to be true, so we dipped into house prices being very high, private rents being extortionate in some cases etc etc, until FB friend concedes that maybe it is a far more complex situation than can be solved by vilifying the single mums. (I was pissed off that he constantly referred to mums rather than single parents tbh.)
Shortly after this discussion came to an end (or so I thought), I get a phone call from my sister, who demands I stop posting (on my own status by this time) because it is upsetting her DD (whose fiance is the FB friend posting on my status
)
This made me rather angry, that I am expected to 'shut up' because my niece is getting upset at her fiance's narrowminded misogynistic view of single mums. (Of course, this will never ever happen to my niece, since FB friend will not be a feckless father ever!!)
I explained to my sister that I would leave it, unless he posted more tripe on my page detailing his uninformed opinion.
He posted again, I decided it wasn't worth the grief.
I have just logged onto my FB to find my other sister's DH (bil) has written that 'house prices are high because many of the top companies have greedy share holders, leading to pay cuts, pay freezes or people losing their jobs therefore adding to the dole queue, hence fewer people pay tax which limits that available to pay out in benefits.' 
Surely this is not the main reason house prices are high?? Or is it??
I am now officially out of my depth and feel a right wally to have started standing up for single mums only to find myself being unable to answer my own bloody status, because of my embarrassing lack of knowledge.
AIBU to be feeling ashamed at my lack of knowledge and a bit pissed off that my sister has asked me to shut up and not defend single mums because it upsets my niece (her DD).